diff options
Diffstat (limited to 'src/datavisualization/engine/shaders/texture3dlowdef.frag')
-rw-r--r-- | src/datavisualization/engine/shaders/texture3dlowdef.frag | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/src/datavisualization/engine/shaders/texture3dlowdef.frag b/src/datavisualization/engine/shaders/texture3dlowdef.frag new file mode 100644 index 00000000..ed0d41ce --- /dev/null +++ b/src/datavisualization/engine/shaders/texture3dlowdef.frag @@ -0,0 +1,109 @@ +#version 120 + +varying highp vec3 pos; +varying highp vec3 rayDir; + +uniform highp sampler3D textureSampler; +uniform highp vec4 colorIndex[256]; +uniform highp int color8Bit; +uniform highp vec3 textureDimensions; +uniform highp int sampleCount; // This is the maximum sample count +uniform highp float alphaMultiplier; +uniform highp int preserveOpacity; +uniform highp vec3 minBounds; +uniform highp vec3 maxBounds; + +// Ray traveling straight through a single 'alpha thickness' applies 100% of the encountered alpha. +// Rays traveling shorter distances apply a fraction. This is used to normalize the alpha over +// entire volume, regardless of texture dimensions +const highp float alphaThicknesses = 32.0; +const highp float SQRT3 = 1.73205081; + +void main() { + vec3 rayStart = pos; + highp vec3 startBounds = minBounds; + highp vec3 endBounds = maxBounds; + if (rayDir.x < 0.0) { + startBounds.x = maxBounds.x; + endBounds.x = minBounds.x; + } + if (rayDir.y > 0.0) { + startBounds.y = maxBounds.y; + endBounds.y = minBounds.y; + } + if (rayDir.z > 0.0) { + startBounds.z = maxBounds.z; + endBounds.z = minBounds.z; + } + + // Calculate ray intersection endpoint + highp vec3 rayStop; + highp vec3 invRayDir = 1.0 / rayDir; + highp vec3 t = (endBounds - rayStart) * invRayDir; + highp float endT = min(t.x, min(t.y, t.z)); + if (endT <= 0.0) + discard; + rayStop = rayStart + endT * rayDir; + + // Convert intersections to texture coords + rayStart = 0.5 * (rayStart + 1.0); + rayStop = 0.5 * (rayStop + 1.0); + + highp vec3 ray = rayStop - rayStart; + + highp float fullDist = length(ray); + highp float stepSize = SQRT3 / sampleCount; + highp vec3 step = (SQRT3 * normalize(ray)) / sampleCount; + + rayStart += (step * 0.001); + + highp vec3 curPos = rayStart; + highp float curLen = 0.0; + highp vec4 curColor = vec4(0, 0, 0, 0); + highp float curAlpha = 0.0; + highp vec3 curRgb = vec3(0, 0, 0); + highp vec4 destColor = vec4(0, 0, 0, 0); + highp float totalOpacity = 1.0; + + highp float extraAlphaMultiplier = stepSize * alphaThicknesses * alphaMultiplier; + + // Raytrace into volume, need to sample pixels along the eye ray until we hit opacity 1 + for (int i = 0; i < sampleCount; i++) { + curColor = texture3D(textureSampler, curPos); + if (color8Bit != 0) + curColor = colorIndex[int(curColor.r * 255.0)]; + + if (curColor.a >= 0.0) { + if (curColor.a == 1.0 && (preserveOpacity == 1 || alphaMultiplier >= 1.0)) + curAlpha = 1.0; + else + curAlpha = curColor.a * extraAlphaMultiplier; + highp float nextOpacity = totalOpacity - curAlpha; + // If opacity goes beyond full opacity, we need to adjust current alpha according + // to the fraction of the distance the material is visible, so that we don't get + // box artifacts around texels. + if (nextOpacity < 0.0) { + curAlpha *= totalOpacity / curAlpha; + nextOpacity = 0.0; + } + + curRgb = curColor.rgb * curAlpha * (totalOpacity + nextOpacity); + destColor.rgb += curRgb; + totalOpacity = nextOpacity; + } + curPos += step; + curLen += stepSize; + if (curLen >= fullDist || totalOpacity <= 0.0) + break; + } + + if (totalOpacity == 1.0) + discard; + + // Brighten up the final color if there is some transparency left + if (totalOpacity >= 0.0 && totalOpacity < 1.0) + destColor *= (1.0 - (totalOpacity * 0.5)) / (1.0 - totalOpacity); + + destColor.a = (1.0 - totalOpacity); + gl_FragColor = clamp(destColor, 0.0, 1.0); +} |