myou-engine/src/graphics/texture.nim

# The contents of this file are subject to the Common Public Attribution License
# Version 1.0 (the “License”); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
# https://myou.dev/licenses/LICENSE-CPAL. The License is based on the Mozilla
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# the Original Developer. In addition, Exhibit A has been modified to be
# consistent with Exhibit B.
#
# Software distributed under the License is distributed on an “AS IS” basis,
# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
# the specific language governing rights and limitations under the License.
#
# The Original Code is Myou Engine.
#
# the Original Developer is the Initial Developer.
#
# The Initial Developer of the Original Code is the Myou Engine developers.
# All portions of the code written by the Myou Engine developers are Copyright
# (c) 2024. All Rights Reserved.
#
# Alternatively, the contents of this file may be used under the terms of the
# GNU Affero General Public License version 3 (the [AGPL-3] License), in which
# case the provisions of [AGPL-3] License are applicable instead of those above.
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# version of this file under either the CPAL or the [AGPL-3] License.

import ../types
import vmath except Quat
import arr_ref
# import tinyre
import std/tables
import ../platform/gl

# Forward declarations
func mipmapHigh*(self: Texture): int
proc needsMipmap*(self: Texture): bool
proc setMaxTextures*(count: int32)
proc newTextureStorage*(ttype: TextureType, width, height, depth: int, format: TextureFormat): TextureStorage
proc preallocate(self: Texture)
proc freeTextureStorage(self: Texture)
proc bind_it*(texture: Texture, reserve_slot: static[int32] = -1, needs_active_texture: static[bool] = false)
proc unbind*(texture: Texture)
proc unbindAllTextures*()
proc destroy*(texture: Texture)
proc loadFromPixelsPointer*(self: Texture, pixels: pointer)
proc loadFromPixels*[T](self: Texture, pixels: SliceMem[T]) {.gcsafe.}
proc loadCubeSideFromPixels*(self: Texture, pixels: pointer, side: int32 = 0)
proc setFilter*(self: Texture, filter: TextureFilter)
proc newTexture*(engine: MyouEngine, name: string, width, height: int, depth: int = 1,
        format: TextureFormat,
        tex_type: TextureType = Tex2D,
        filter: TextureFilter = Trilinear,
        pixels: ArrRef[float32] = nil): Texture
proc generateMipmap*(self: Texture)
func to_sRGB*(format: TextureFormat): TextureFormat
proc newTexture*(engine: MyouEngine, name: string, data: SliceMem[byte],
                is_sRGB: bool, filter: TextureFilter = Trilinear, depth=1,
                flip = true, use_compression = true): Texture
proc newTexture*(engine: MyouEngine, name: string, file_name: string, is_sRGB: bool,
        filter: TextureFilter = Trilinear,
        tex_type: TextureType = Tex2D,
        flip = true,
        use_compression = true,
    ): Texture
proc setExtrapolation*(self: Texture, ext: TextureExtrapolation)
proc getTexturePixels*(self: Texture): TexturePixels
proc setMipmapRange*(self: Texture, first = 0, last = 1000) {.gcsafe.}
func vec3size*(self: Texture, mip_level = -1): Vec3
func toInternalFormat*(format: TextureFormat): GLenum
# End forward declarations

# import sugar

import std/bitops
import std/strformat
import loadable
import dds_ktx
import ../gpu_formats/texture_decode
import ../gpu_formats/texture_optimize

# TODO: use and test destructor

# NOTE: we moved this from the render manager to global state
# (if we ever need multiple instances with different context
# we should move them back)
# NOTE: set as threadvar for optimization (and for having procs gcsafe
# implicitely), we only use them in the main thread
var bound_textures {.threadvar.}: seq[Texture]
var active_texture {.threadvar.}: int32
var next_texture {.threadvar.}: int32
var max_textures {.threadvar.}: int32
var reserved {.threadvar.}: int32
active_texture = -1

if defined(android):
    # I don't know why slot 0 makes the mesh not render at all
    # TODO: maybe it only happens when building with ArCore support
    # even if it's not used, we should test it
    reserved = 1

func samplerType*(tex_type: TextureType): string =
    case tex_type:
        of Tex2D: "sampler2D"
        of Tex2DArray: "sampler2DArray"
        of Tex3D: "sampler3D"
        of TexCube: "samplerCube"
        of TexExternal: "samplerExternalOES" ## NOTE: requires GLSL extension

template samplerType*(self: Texture): string = self.tex_type.samplerType

func toInternalFormat*(format: TextureFormat): GLenum =
    case format:
        of SRGB_u8: GL_SRGB8
        of SRGB_Alpha_u8: GL_SRGB8_ALPHA8
        of R_u8: GL_R8
        of RG_u8: GL_RG8
        of RGB_u8: GL_RGB8
        of RGBA_u8: GL_RGBA8
        of R_u16: GL_R16_EXT
        of RG_u16: GL_RG16_EXT
        of RGB_u16: GL_RGB16_EXT
        of RGBA_u16: GL_RGBA16_EXT
        of R_f16: GL_R16F
        of RG_f16: GL_RG16F
        of RGB_f16: GL_RGB16F
        of RGBA_f16: GL_RGBA16F
        of R_f32: GL_R32F
        of RG_f32: GL_RG32F
        of RGB_f32: GL_RGB32F
        of RGBA_f32: GL_RGBA32F
        of Depth_u16: GL_DEPTH_COMPONENT16
        of Depth_u24: GL_DEPTH_COMPONENT24
        # of Depth_u24_s8: 0x81A7.GLenum
        of Depth_f32: GL_DEPTH_COMPONENT32F
        # else:
        #     raise newException(ValueError, "Unsupported format")

# To change with bindless textures
func texturesNeedBinding*(): bool {.inline.} = true

func mipmapHigh*(self: Texture): int =
    let depth = if self.tex_type == Tex2DArray: 1 else: self.depth
    floor(log2(max(max(self.width, self.height), depth).float32)).int

func mipmapCount*(self: Texture): int = self.mipmapHigh + 1

proc needsMipmap*(self: Texture): bool =
    case self.filter:
        of Nearest, Linear: false
        else: true

# TODO: this is hacky
# instead we should query the GL API the first time we need this
# or to make a texture manager class
proc setMaxTextures*(count: int32) =
    max_textures = count
    assert max_textures != 0
    bound_textures.setLen max_textures

proc setTextureReservedSlots*(reserved_slots_bitfield: int32) =
    reserved = reserved_slots_bitfield

proc resetNextTextureSlot*() =
    next_texture = 0

proc newTextureStorage*(ttype: TextureType, width, height, depth: int, format: TextureFormat): TextureStorage =
    var ts = new TextureStorage
    ts.unit = -1
    ts.target = case ttype:
        of Tex2D: GL_TEXTURE_2D
        of Tex2DArray: GL_TEXTURE_2D_ARRAY
        of Tex3D: GL_TEXTURE_3D
        of TexCube: GL_TEXTURE_CUBE_MAP
        of TexExternal: GL_TEXTURE_EXTERNAL_OES
    ts.iformat = format.toInternalFormat
    ts.format = case format:
        of R_u8, R_u16, R_f16, R_f32: GL_RED
        of RG_u8, RG_u16, RG_f16, RG_f32: GL_RG
        of SRGB_u8, RGB_u8, RGB_u16, RGB_f16, RGB_f32: GL_RGB
        of SRGB_Alpha_u8, RGBA_u8, RGBA_u16, RGBA_f16, RGBA_f32: GL_RGBA
        of Depth_u16, Depth_u24, Depth_f32: GL_DEPTH_COMPONENT
        # of Depth_u24_s8: GL_DEPTH_COMPONENT
        # else:
        #     raise newException(ValueError, "Unsupported format")
    ts.gltype = case format:
        of SRGB_u8, SRGB_Alpha_u8, R_u8, RG_u8, RGB_u8, RGBA_u8: GL_UNSIGNED_BYTE
        of R_f16, RG_f16, RGB_f16, RGBA_f16: GL_HALF_FLOAT
        of R_f32, RG_f32, RGB_f32, RGBA_f32, Depth_f32: cGL_FLOAT
        of R_u16, RG_u16, RGB_u16, RGBA_u16, Depth_u16: GL_UNSIGNED_SHORT
        of Depth_u24: GL_UNSIGNED_INT
        # of Depth_u24_s8: GL_UNSIGNED_INT
    ts.layer = 0
    ts.tile_size = vec2(1,1)
    var tex: GLuint
    glGenTextures(1, addr tex)
    ts.tex = tex.GPUTexture
    return ts

proc preallocate(self: Texture) =
    let ts {.cursor.} = self.storage
    case self.tex_type:
    of Tex2D:
        # TODO: only do this if necessary
        for m in 0 .. self.mipmapHigh:
            glTexImage2D(ts.target, m.GLint, ts.iformat.GLint,
                max(1, self.width.GLsizei shr m), max(1, self.height.GLsizei shr m),
                0, ts.format, ts.gltype, nil)
    of Tex2DArray:
        # TODO: only do this if necessary
        for m in 0 .. self.mipmapHigh:
            glTexImage3D(ts.target, m.GLint, ts.iformat.GLint,
                max(1, self.width.GLsizei shr m),
                max(1, self.height.GLsizei shr m),
                self.depth.GLsizei,
                0, ts.format, ts.gltype, nil)
    of Tex3D:
        # TODO: only do this if necessary
        for m in 0 .. self.mipmapHigh:
            glTexImage3D(ts.target, m.GLint, ts.iformat.GLint,
                max(1, self.width.GLsizei shr m),
                max(1, self.height.GLsizei shr m),
                max(1, self.depth.GLsizei shr m),
                0, ts.format, ts.gltype, nil)
    of TexCube:
        for m in 0 .. self.mipmapHigh:
            for i in GL_TEXTURE_CUBE_MAP_POSITIVE_X.GLuint .. GL_TEXTURE_CUBE_MAP_NEGATIVE_Z.GLuint:
                glTexImage2D(i.GLenum, m.GLint, ts.iformat.GLint,
                    max(1, self.width.GLsizei shr m), max(1, self.height.GLsizei shr m),
                    0, ts.format, ts.gltype, nil)
    of TexExternal:
        discard

proc freeTextureStorage(self: Texture) =
    self.storage = nil

proc bind_it*(texture: Texture, reserve_slot: static[int32] = -1, needs_active_texture: static[bool] = false) =
    # TODO: rewrite for using texture arrays and/or bindless
    if texture.storage.unit == -1:
        when reserve_slot >= 0:
            let bound_unit = reserve_slot
            reserved.setbit bound_unit
        else:
            while reserved.testbit next_texture:
                inc(next_texture)
                if next_texture == max_textures:
                    next_texture = 0
            let bound_unit = next_texture
        texture.storage.unit = bound_unit
        if active_texture != bound_unit:
            active_texture = bound_unit
            glActiveTexture(cast[GLenum](GL_TEXTURE0.uint32 + bound_unit.uint32))
        var old_tex {.cursor.} = bound_textures[bound_unit]
        if old_tex != nil:
            old_tex.storage.unit = -1
            if old_tex.storage.target.uint32 != texture.storage.target.uint32:
                glBindTexture(old_tex.storage.target, 0)
            # if old_tex.sampler_object != 0:
            #     glBindSampler(cast[GLuint](bound_unit), 0)
            bound_textures[bound_unit] = nil
        glBindTexture(texture.storage.target, GLuint(texture.storage.tex))
        # if texture.sampler_object != 0:
        #     glBindSampler(bound_unit.GLuint, texture.sampler_object)
        bound_textures[bound_unit] = texture
        inc(next_texture)
        if next_texture == max_textures:
            next_texture = 0
    else:
        when needs_active_texture:
            if active_texture != texture.storage.unit:
                active_texture = texture.storage.unit
                glActiveTexture((GL_TEXTURE0.uint32 + texture.storage.unit.uint32).GLenum)

proc unbind*(texture: Texture) =
    if texture.storage.unit == -1:
        return
    let bound_unit = texture.storage.unit
    var old_tex {.cursor.} = bound_textures[bound_unit]
    assert old_tex == texture, "unexpected bound texture"
    if old_tex == texture:
        bound_textures[bound_unit] = nil
        active_texture = bound_unit
        glActiveTexture((GL_TEXTURE0.uint32 + bound_unit.uint32).GLenum)
        glBindTexture(texture.storage.target, 0)
        if texture.sampler_object != 0:
            glBindSampler(bound_unit.GLuint, 0)
        texture.storage.unit = -1
        texture.last_used_shader = nil
        reserved.clearbit bound_unit

proc bind_all*(textures: seq[Texture], locations: seq[GLint]) =
    # TODO: if not loaded, put a blank texture instead
    var used = reserved
    for t in textures:
        let unit = t.storage.unit
        if unit != -1:
            used.setbit unit
    for i,texture in textures:
        var unit = texture.storage.unit
        if unit == -1:
            while used.testbit next_texture:
                inc(next_texture)
                if next_texture == max_textures:
                    next_texture = 0
            unit = next_texture
            active_texture = unit
            texture.storage.unit = unit
            glActiveTexture(cast[GLenum](GL_TEXTURE0.uint32 + unit.uint32))
            let old_tex {.cursor.} = bound_textures[unit]
            if old_tex != nil:
                old_tex.storage.unit = -1
                if old_tex.storage.target != texture.storage.target:
                    glBindTexture(old_tex.storage.target, 0)
            glBindTexture(texture.storage.target, texture.storage.tex.GLuint)
            bound_textures[unit] = texture
            inc(next_texture)
            if next_texture == max_textures:
                next_texture = 0
        glUniform1i(locations[i], unit)

proc unbindAllTextures*() =
    for tex in bound_textures:
        if tex != nil:
            tex.unbind()
    next_texture = 0

proc destroy*(texture: Texture) =
    if texture.storage != nil:
        texture.unbind()
        texture.freeTextureStorage()

proc loadFromPixelsPointer*(self: Texture, pixels: pointer) =
    let ts = self.storage
    self.loaded = true
    self.bind_it(needs_active_texture=true)
    when not defined(release):
        assert self.tex_type notin [TexCube, TexExternal]
    if self.depth == 1:
        glTexImage2D(ts.target, 0, ts.iformat.GLint,
            self.width.GLsizei, self.height.GLsizei,
            0, ts.format, ts.gltype, pixels)
    else:
        glTexImage3D(ts.target, 0, ts.iformat.GLint,
            self.width.GLsizei, self.height.GLsizei, self.depth.GLsizei,
            0, ts.format, ts.gltype, pixels)
    if self.needsMipmap:
        glGenerateMipmap(ts.target)

proc loadFromPixels*[T](self: Texture, pixels: SliceMem[T]) {.gcsafe.} =
    self.loadFromPixelsPointer(pixels.data)

proc loadCubeSideFromPixels*(self: Texture, pixels: pointer, side: int32 = 0) =
    let ts = self.storage
    self.loaded = true
    self.bind_it(needs_active_texture=true)
    when not defined(release):
        assert self.tex_type == TexCube
    glTexImage2D((GL_TEXTURE_CUBE_MAP_POSITIVE_X.GLuint + cast[GLuint](side)).GLenum, 0, ts.iformat.GLint,
        self.width.GLsizei, self.height.GLsizei,
        0, ts.format, ts.gltype, pixels)

proc loadCompressedData*(self: Texture, data: KtxInfoParts, refdata: seq[SliceMem[byte]]) {.gcsafe.} =
    assert data.info.depth == 1 and data.info.num_layers == 1,
        "Compressed array and 3D textures not supported yet"
    let ts = self.storage
    self.loaded = true
    self.bind_it(needs_active_texture=true)
    let target = if self.tex_type == TexCube: GL_TEXTURE_CUBE_MAP_POSITIVE_X.GLuint.int32
    else: ts.target.GLuint.int32
    for part in data.parts:
        glCompressedTexImage2D(cast[GLenum](target+part.face), part.mip_level,
            data.info.internal_format.GLenum, part.width.GLsizei, part.height.GLsizei,
            0, part.len.GLsizei, part.data)
    self.setMipmapRange(0, data.info.num_mipmaps - 1)

proc setFilter*(self: Texture, filter: TextureFilter) =
    self.filter = filter
    self.engine.renderer.enqueue proc()=
        if self.storage == nil: return
        let min_filter = case filter
            of Nearest: GL_NEAREST
            of Pixellated: GL_NEAREST_MIPMAP_NEAREST
            of Linear: GL_LINEAR
            of Trilinear, Anisotropic: GL_LINEAR_MIPMAP_LINEAR
        let mag_filter = case filter
            of Nearest, Pixellated: GL_NEAREST
            else: GL_LINEAR
        self.bind_it(needs_active_texture=true)
        glTexParameteri(self.storage.target, GL_TEXTURE_MAG_FILTER, mag_filter.GLint)
        glTexParameteri(self.storage.target, GL_TEXTURE_MIN_FILTER, min_filter.GLint)

proc ensure_storage*(self: Texture) =
    if self.storage == nil:
        self.storage = newTextureStorage(self.tex_type, self.width, self.height, self.depth, self.format)
        self.setFilter self.filter
        self.mipmap_range = (0, self.mipmapHigh)

proc newTexture*(engine: MyouEngine, name: string,
        width, height: int; depth: int = 1,
        format: TextureFormat,
        tex_type: TextureType = Tex2D,
        filter: TextureFilter = Trilinear,
        pixels: ArrRef[float32] = nil): Texture =
    result = new Texture
    result.engine = engine
    result.name = name
    result.tex_type = tex_type
    result.format = format
    result.width = width
    result.height = height
    result.depth = depth
    if tex_type == TexCube:
        assert width == height
        result.depth = width
    result.filter = filter
    if width != 0 and height != 0:
        let self = result
        self.engine.renderer.enqueue proc()=
            self.ensure_storage()
            if pixels != nil:
                self.loadFromPixelsPointer(pixels.toPointer)
            else:
                self.preallocate()
            when defined(myouUseRenderdoc):
                # Note: when we switch to arrays we'll have to store resolutions
                # instead of names
                glObjectLabel(GL_TEXTURE, self.storage.tex.GLuint,
                            GLsizei(self.name.len), self.name.cstring)

proc generateMipmap*(self: Texture) =
    assert self.tex_type != TexExternal
    self.bind_it(needs_active_texture=true)
    glGenerateMipmap(self.storage.target)

func to_sRGB*(format: TextureFormat): TextureFormat =
    return case format:
        of RGBA_u8: SRGB_Alpha_u8
        of RGB_u8: SRGB_u8
        else: raise newException(ValueError, "There's no sRGB version of " & $format)

proc newTexture*(engine: MyouEngine, name: string, data: SliceMem[byte],
                is_sRGB: bool, filter: TextureFilter = Trilinear, depth=1,
                flip = true, use_compression = true): Texture =
    var (width, height, format) = getDimensionsFormat(data.data, data.byte_len)
    if is_sRGB:
        if format in [RGB_u8, RGBA_u8]:
            format = format.to_sRGB
        else:
            # TODO: sRGB shader for 1 and 2 channel textures
            echo &"WARNING: Texture {name} is sRGB but has format {format} _"
    let self = engine.newTexture(name, width, height, depth, format, filter=filter)
    self.is_sRGB = is_sRGB
    engine.renderer.enqueue proc() =
        if use_compression:
            self.loadOptimizedThreaded(@[data], loadFromPixels, loadCompressedData)
        else:
            self.loadOptimizedThreaded(@[data], loadFromPixels, nil)
    return self

proc newTexture*(engine: MyouEngine, name: string, file_name: string, is_sRGB: bool,
        filter: TextureFilter = Trilinear,
        tex_type: TextureType = Tex2D,
        flip = true,
        use_compression = true,
    ): Texture =

    # TODO: Api that stores the LoadableResource so it can be re-loaded later
    # note: format does not matter at this point, will be replaced later
    let self = engine.newTexture(name, 0, 0, filter=filter, format=RGBA_u8, tex_type=tex_type)
    self.is_sRGB = is_sRGB
    var res: LoadableResource
    proc load(ok: bool, err: string, data: SliceMem[byte]) =
        assert ok, &"Error loading texture '{self.name}' from '{file_name}': {err}"
        let ktx_info = GetDdsKtxInfo(data.data, data.byte_len)
        if ktx_info.isSome:
            let ktx_info = ktx_info.get
            assert ktx_info.is_cubemap == (self.tex_type == TexCube)
            self.width = ktx_info.width
            self.height = ktx_info.height
            self.depth = ktx_info.depth
            self.format = if ktx_info.has_alpha: RGBA_u8 else: RGB_u8
            if ktx_info.is_sRGB:
                self.format = self.format.to_sRGB
            engine.renderer.enqueue proc()=
                try:
                    self.ensure_storage()
                    let info_parts = KtxInfoParts(
                        info: ktx_info,
                        parts: ParseDdsKtx(data.data, data.byte_len))
                    self.loadCompressedData(info_parts, @[data])
                    self.loaded = true
                # except Exception as e:
                except:
                    # TODO: use logging
                    # for line in e.getStackTrace.split '\n':
                    #     echo line
                    echo getCurrentExceptionMsg()
                    echo "Error loading texture " & file_name
        else:
            var (width, height, format) = getDimensionsFormat(data.data, data.byte_len, 3)
            if is_sRGB:
                if format in [RGB_u8, RGBA_u8]:
                    format = format.to_sRGB
                else:
                    # TODO: sRGB shader for 1 and 2 channel textures
                    echo &"WARNING: Texture {self.name} is sRGB but has format {format}"
            self.width = width
            self.height = height
            self.format = format
            engine.renderer.enqueue proc()=
                try:
                    self.ensure_storage()
                    if use_compression:
                        self.loadOptimizedThreaded(@[data], loadFromPixels, loadCompressedData)
                    else:
                        self.loadOptimizedThreaded(@[data], loadFromPixels, nil)
                except:
                    # TODO: use logging
                    echo getCurrentExceptionMsg()
                    echo "Error loading texture " & file_name
    res = file_name.loadUri(load, auto_start=false)
    res.start()
    return self

proc setExtrapolation*(self: Texture, ext: TextureExtrapolation) =
    let e = case ext:
        of Clamp: GL_CLAMP_TO_EDGE
        of Border: GL_CLAMP_TO_BORDER
        of Repeat: GL_REPEAT
        of MirroredRepeat: GL_MIRRORED_REPEAT
    self.engine.renderer.enqueue proc()=
        self.bind_it(needs_active_texture=true)
        glTexParameteri(self.storage.target, GL_TEXTURE_WRAP_S, e.GLint)
        glTexParameteri(self.storage.target, GL_TEXTURE_WRAP_T, e.GLint)
        glTexParameteri(self.storage.target, GL_TEXTURE_WRAP_R, e.GLint)

proc getTexturePixels*(self: Texture): TexturePixels =
    when false:
        var len_bytes, cube_stride = self.width * self.height * self.format.stride
        if self.tex_type == TexCube:
            len_bytes *= 6
        result.pixels = newArrRef[int8](len_bytes).to(float32)
        result.width = self.width
        result.height = self.height
        result.format = self.format
        result.tex_type = self.tex_type
        self.bind_it(needs_active_texture=true)
        if self.tex_type == TexCube:
            var p = cast[ptr UncheckedArray[int8]](result.pixels.toPointer)
            var pos = 0
            for i in GL_TEXTURE_CUBE_MAP_POSITIVE_X.GLuint .. GL_TEXTURE_CUBE_MAP_NEGATIVE_Z.GLuint:
                glGetTexImage(i.GLenum, 0, self.storage.format, self.storage.gltype,
                    p[pos].addr)
                pos += cube_stride
        else:
            glGetTexImage(self.storage.target, 0, self.storage.format, self.storage.gltype, result.pixels.toPointer)

# TODO: limit the amount of mip maps to save some draw calls
# (e.g. minimum resolution 16x16 for blurred mipmaps)

proc setMipmapRange*(self: Texture, first = 0, last = 1000) {.gcsafe.} =
    self.bind_it(needs_active_texture=true)
    self.mipmap_range = (first, last)
    glTexParameteri(self.storage.target, GL_TEXTURE_BASE_LEVEL, first.GLint);
    glTexParameteri(self.storage.target, GL_TEXTURE_MAX_LEVEL, last.GLint);

func vec3size*(self: Texture, mip_level = -1): Vec3 =
    let depth = if self.tex_type == Tex2DArray: 1 else: self.depth
    let mip_level = if mip_level != -1: mip_level
    else: self.mipmap_range[0]
    vec3((max(1, self.width shr mip_level)).float32, 
        (max(1, self.height shr mip_level)).float32, 
        (max(1, depth shr mip_level)).float32)

proc set_texture_shadow*(self: Texture) =
    self.bind_it(needs_active_texture=true)
    if self.format in [Depth_u16, Depth_u24, Depth_f32]:
        glTexParameteri(self.storage.target, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_REF_TO_TEXTURE.GLint)
        # TODO: would GL_LESS be better? That way depth 1.0 would always be not in shadow
        # so we wouldn't need to clamp in shader
        glTexParameteri(self.storage.target, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL.GLint)

proc unset_texture_shadow*(self: Texture) =
    self.bind_it(needs_active_texture=true)
    glTexParameteri(self.storage.target, GL_TEXTURE_COMPARE_MODE, GL_NONE.GLint)