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https://github.com/bevyengine/bevy
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# Objective - It's often really useful to have access to the time when writing shaders. ## Solution - Add a UnifformBuffer in the mesh view bind group - This buffer contains the time, delta time and a wrapping frame count https://user-images.githubusercontent.com/8348954/180130314-97948c2a-2d11-423d-a9c4-fb5c9d1892c7.mp4 --- ## Changelog - Added a `GlobalsUniform` at position 9 of the mesh view bind group ## Notes The implementation is currently split between bevy_render and bevy_pbr because I was basing my implementation on the `ViewPlugin`. I'm not sure if that's the right way to structure it. I named this `globals` instead of just time because we could potentially add more things to it. ## References in other engines - Godot: <https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/canvas_item_shader.html#global-built-ins> - Global time since startup, in seconds, by default resets to 0 after 3600 seconds - Doesn't seem to have anything else - Unreal: <https://docs.unrealengine.com/4.26/en-US/RenderingAndGraphics/Materials/ExpressionReference/Constant/> - Generic time value that updates every frame. Can be paused or scaled. - Frame count node, doesn't seem to be an equivalent for shaders: <https://docs.unrealengine.com/4.26/en-US/BlueprintAPI/Utilities/GetFrameCount/> - Unity: <https://docs.unity3d.com/Manual/SL-UnityShaderVariables.html> - time since startup in seconds. No mention of time wrapping. Stored as a `vec4(t/20, t, t*2, t*3)` where `t` is the value in seconds - Also has delta time, sin time and cos time - ShaderToy: <https://www.shadertoy.com/howto> - iTime is the time since startup in seconds. - iFrameRate - iTimeDelta - iFrame frame counter Co-authored-by: Charles <IceSentry@users.noreply.github.com>
47 lines
1.6 KiB
WebGPU Shading Language
47 lines
1.6 KiB
WebGPU Shading Language
#import bevy_pbr::mesh_types
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// The time since startup data is in the globals binding which is part of the mesh_view_bindings import
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#import bevy_pbr::mesh_view_bindings
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fn oklab_to_linear_srgb(c: vec3<f32>) -> vec3<f32> {
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let L = c.x;
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let a = c.y;
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let b = c.z;
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let l_ = L + 0.3963377774 * a + 0.2158037573 * b;
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let m_ = L - 0.1055613458 * a - 0.0638541728 * b;
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let s_ = L - 0.0894841775 * a - 1.2914855480 * b;
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let l = l_ * l_ * l_;
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let m = m_ * m_ * m_;
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let s = s_ * s_ * s_;
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return vec3<f32>(
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4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s,
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-1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s,
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-0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s,
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);
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}
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struct FragmentInput {
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#import bevy_pbr::mesh_vertex_output
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}
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@fragment
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fn fragment(in: FragmentInput) -> @location(0) vec4<f32> {
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let speed = 2.0;
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// The globals binding contains various global values like time
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// which is the time since startup in seconds
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let t_1 = sin(globals.time * speed) * 0.5 + 0.5;
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let t_2 = cos(globals.time * speed);
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let distance_to_center = distance(in.uv, vec2<f32>(0.5)) * 1.4;
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// blending is done in a perceptual color space: https://bottosson.github.io/posts/oklab/
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let red = vec3<f32>(0.627955, 0.224863, 0.125846);
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let green = vec3<f32>(0.86644, -0.233887, 0.179498);
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let blue = vec3<f32>(0.701674, 0.274566, -0.169156);
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let white = vec3<f32>(1.0, 0.0, 0.0);
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let mixed = mix(mix(red, blue, t_1), mix(green, white, t_2), distance_to_center);
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return vec4<f32>(oklab_to_linear_srgb(mixed), 1.0);
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}
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