struct Uniforms { | |
u_scale : vec2<f32>; | |
u_offset : vec2<f32>; | |
}; | |
[[binding(0), group(0)]] var<uniform> uniforms : Uniforms; | |
struct VertexOutputs { | |
[[location(0)]] texcoords : vec2<f32>; | |
[[builtin(position)]] position : vec4<f32>; | |
}; | |
[[stage(vertex)]] fn vs_main( | |
[[builtin(vertex_index)]] VertexIndex : u32 | |
) -> VertexOutputs { | |
var texcoord = array<vec2<f32>, 3>( | |
vec2<f32>(-0.5, 0.0), | |
vec2<f32>( 1.5, 0.0), | |
vec2<f32>( 0.5, 2.0)); | |
var output : VertexOutputs; | |
output.position = vec4<f32>((texcoord[VertexIndex] * 2.0 - vec2<f32>(1.0, 1.0)), 0.0, 1.0); | |
// Y component of scale is calculated by the copySizeHeight / textureHeight. Only | |
// flipY case can get negative number. | |
var flipY = uniforms.u_scale.y < 0.0; | |
// Texture coordinate takes top-left as origin point. We need to map the | |
// texture to triangle carefully. | |
if (flipY) { | |
// We need to get the mirror positions(mirrored based on y = 0.5) on flip cases. | |
// Adopt transform to src texture and then mapping it to triangle coord which | |
// do a +1 shift on Y dimension will help us got that mirror position perfectly. | |
output.texcoords = (texcoord[VertexIndex] * uniforms.u_scale + uniforms.u_offset) * | |
vec2<f32>(1.0, -1.0) + vec2<f32>(0.0, 1.0); | |
} else { | |
// For the normal case, we need to get the exact position. | |
// So mapping texture to triangle firstly then adopt the transform. | |
output.texcoords = (texcoord[VertexIndex] * | |
vec2<f32>(1.0, -1.0) + vec2<f32>(0.0, 1.0)) * | |
uniforms.u_scale + uniforms.u_offset; | |
} | |
return output; | |
} | |
[[binding(1), group(0)]] var mySampler: sampler; | |
[[binding(2), group(0)]] var myTexture: texture_2d<f32>; | |
[[stage(fragment)]] fn fs_main( | |
[[location(0)]] texcoord : vec2<f32> | |
) -> [[location(0)]] vec4<f32> { | |
// Clamp the texcoord and discard the out-of-bound pixels. | |
var clampedTexcoord = | |
clamp(texcoord, vec2<f32>(0.0, 0.0), vec2<f32>(1.0, 1.0)); | |
if (!all(clampedTexcoord == texcoord)) { | |
discard; | |
} | |
var srcColor = textureSample(myTexture, mySampler, texcoord); | |
// Swizzling of texture formats when sampling / rendering is handled by the | |
// hardware so we don't need special logic in this shader. This is covered by tests. | |
return srcColor; | |
} |