92 lines
2.9 KiB
Text
92 lines
2.9 KiB
Text
#version 450
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layout (local_size_x = 16, local_size_y = 16) in;
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layout(rgba8,set = 0, binding = 0) uniform image2D image;
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// License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
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//push constants block
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layout( push_constant ) uniform constants
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{
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vec4 data1;
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vec4 data2;
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vec4 data3;
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vec4 data4;
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} PushConstants;
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// Return random noise in the range [0.0, 1.0], as a function of x.
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float Noise2d( in vec2 x )
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{
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float xhash = cos( x.x * 37.0 );
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float yhash = cos( x.y * 57.0 );
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return fract( 415.92653 * ( xhash + yhash ) );
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}
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// Convert Noise2d() into a "star field" by stomping everthing below fThreshhold to zero.
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float NoisyStarField( in vec2 vSamplePos, float fThreshhold )
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{
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float StarVal = Noise2d( vSamplePos );
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if ( StarVal >= fThreshhold )
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StarVal = pow( (StarVal - fThreshhold)/(1.0 - fThreshhold), 6.0 );
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else
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StarVal = 0.0;
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return StarVal;
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}
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// Stabilize NoisyStarField() by only sampling at integer values.
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float StableStarField( in vec2 vSamplePos, float fThreshhold )
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{
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// Linear interpolation between four samples.
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// Note: This approach has some visual artifacts.
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// There must be a better way to "anti alias" the star field.
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float fractX = fract( vSamplePos.x );
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float fractY = fract( vSamplePos.y );
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vec2 floorSample = floor( vSamplePos );
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float v1 = NoisyStarField( floorSample, fThreshhold );
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float v2 = NoisyStarField( floorSample + vec2( 0.0, 1.0 ), fThreshhold );
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float v3 = NoisyStarField( floorSample + vec2( 1.0, 0.0 ), fThreshhold );
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float v4 = NoisyStarField( floorSample + vec2( 1.0, 1.0 ), fThreshhold );
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float StarVal = v1 * ( 1.0 - fractX ) * ( 1.0 - fractY )
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+ v2 * ( 1.0 - fractX ) * fractY
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+ v3 * fractX * ( 1.0 - fractY )
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+ v4 * fractX * fractY;
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return StarVal;
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}
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void mainImage( out vec4 fragColor, in vec2 fragCoord )
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{
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vec2 iResolution = imageSize(image);
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// Sky Background Color
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//vec3 vColor = vec3( 0.1, 0.2, 0.4 ) * fragCoord.y / iResolution.y;
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vec3 vColor = PushConstants.data1.xyz * fragCoord.y / iResolution.y;
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// Note: Choose fThreshhold in the range [0.99, 0.9999].
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// Higher values (i.e., closer to one) yield a sparser starfield.
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float StarFieldThreshhold = PushConstants.data1.w;//0.97;
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// Stars with a slow crawl.
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float xRate = 0.2;
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float yRate = -0.06;
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vec2 vSamplePos = fragCoord.xy + vec2( xRate * float( 1 ), yRate * float( 1 ) );
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float StarVal = StableStarField( vSamplePos, StarFieldThreshhold );
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vColor += vec3( StarVal );
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fragColor = vec4(vColor, 1.0);
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}
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void main()
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{
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vec4 value = vec4(0.0, 0.0, 0.0, 1.0);
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ivec2 texelCoord = ivec2(gl_GlobalInvocationID.xy);
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ivec2 size = imageSize(image);
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if(texelCoord.x < size.x && texelCoord.y < size.y)
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{
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vec4 color;
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mainImage(color,texelCoord);
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imageStore(image, texelCoord, color);
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}
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}
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