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// Ref: https://gist.github.com/TheRealMJP/c83b8c0f46b63f3a88a5986f4fa982b1 from MJP |
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// Samples a texture with Catmull-Rom filtering, using 9 texture fetches instead of 16. |
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// See http://vec3.ca/bicubic-filtering-in-fewer-taps/ for more details |
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float4 SampleTextureCatmullRom(TEXTURE2D_ARGS(tex, linearSampler), float2 uv, float2 texSize) |
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{ |
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// We're going to sample a a 4x4 grid of texels surrounding the target UV coordinate. We'll do this by rounding |
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// down the sample location to get the exact center of our "starting" texel. The starting texel will be at |
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// location [1, 1] in the grid, where [0, 0] is the top left corner. |
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float2 samplePos = uv * texSize; |
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float2 texPos1 = floor(samplePos - 0.5f) + 0.5f; |
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// Compute the fractional offset from our starting texel to our original sample location, which we'll |
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// feed into the Catmull-Rom spline function to get our filter weights. |
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float2 f = samplePos - texPos1; |
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float2 f2 = f * f; |
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float2 f3 = f2 * f; |
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// Compute the Catmull-Rom weights using the fractional offset that we calculated earlier. |
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// These equations are pre-expanded based on our knowledge of where the texels will be located, |
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// which lets us avoid having to evaluate a piece-wise function. |
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float2 w0 = (1.0f / 6.0) * (-3.0 * f3 + 6.0 * f2 - 3.0 * f); |
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float2 w1 = (1.0f / 6.0) * (9.0 * f3 - 15.0 * f2 + 6.0); |
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float2 w2 = (1.0f / 6.0) * (-9.0 * f3 + 12.0 * f2 + 3.0 * f); |
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float2 w3 = (1.0f / 6.0) * (3.0 * f3 - 3.0 * f2); |
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// Otim by Vlad, to test |
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// float2 w0 = (1.0 / 2.0) * f * (-1.0 + f * (2.0 - f)); |
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// float2 w1 = (1.0 / 6.0) * f2 * (-15.0 + 9.0 * f)) + 1.0; |
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// float2 w2 = (1.0 / 6.0) * f * (3.0 + f * (12.0 - f * 9.0)); |
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// float2 w3 = (1.0 / 2.0) * f2 * (f - 1.0); |
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// Work out weighting factors and sampling offsets that will let us use bilinear filtering to |
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// simultaneously evaluate the middle 2 samples from the 4x4 grid. |
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float2 w12 = w1 + w2; |
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float2 offset12 = w2 / (w1 + w2); |
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// Compute the final UV coordinates we'll use for sampling the texture |
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float2 texPos0 = texPos1 - 1; |
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float2 texPos3 = texPos1 + 2; |
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float2 texPos12 = texPos1 + offset12; |
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texPos0 /= texSize; |
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texPos3 /= texSize; |
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texPos12 /= texSize; |
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float4 result = 0.0; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos0.x, texPos0.y), 0.0) * w0.x * w0.y; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos12.x, texPos0.y), 0.0) * w12.x * w0.y; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos3.x, texPos0.y), 0.0) * w3.x * w0.y; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos0.x, texPos12.y), 0.0) * w0.x * w12.y; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos12.x, texPos12.y), 0.0) * w12.x * w12.y; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos3.x, texPos12.y), 0.0) * w3.x * w12.y; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos0.x, texPos3.y), 0.0) * w0.x * w3.y; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos12.x, texPos3.y), 0.0) * w12.x * w3.y; |
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result += TEXTURE2D_SAMPLE_LOD(tex, linearSampler, float2(texPos3.x, texPos3.y), 0.0) * w3.x * w3.y; |
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return result; |
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} |
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/* |
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// manual tri-linearly interpolated texture fetch |
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// not really needed: used hard-wired texture interpolation |
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vec4 manualTexture3D( sampler3D samp, vec3 p ){ |
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vec3 qa = p*uvMapSize + vec3(0.5); |
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vec3 qi = floor(qa); |
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qa -= qi; |
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qi -= vec3(0.5); |
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return |
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mix( mix( mix( texture3D( samp, (qi+vec3(0.0,0.0,0.0))*oneOverUvMapSize ), |
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texture3D( samp, (qi+vec3(1.0,0.0,0.0))*oneOverUvMapSize ), qa.x ), |
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mix( texture3D( samp, (qi+vec3(0.0,1.0,0.0))*oneOverUvMapSize ), |
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texture3D( samp, (qi+vec3(1.0,1.0,0.0))*oneOverUvMapSize ), qa.x ), qa.y ), |
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mix( mix( texture3D( samp, (qi+vec3(0.0,0.0,1.0))*oneOverUvMapSize ), |
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texture3D( samp, (qi+vec3(1.0,0.0,1.0))*oneOverUvMapSize ), qa.x ), |
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mix( texture3D( samp, (qi+vec3(0.0,1.0,1.0))*oneOverUvMapSize ), |
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texture3D( samp, (qi+vec3(1.0,1.0,1.0))*oneOverUvMapSize ), qa.x ), qa.y ), qa.z ); |
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} |
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*/ |
Remy
7 年前