1 files changed, 70 insertions, 0 deletions
diff --git a/src/datavisualization/engine/shaders/texture3d.frag b/src/datavisualization/engine/shaders/texture3d.frag
new file mode 100644
index 00000000..054b59cb
--- /dev/null
+++ b/src/datavisualization/engine/shaders/texture3d.frag
@@ -0,0 +1,70 @@
+#version 120
+
+varying highp vec3 pos;
+
+uniform highp sampler3D textureSampler;
+uniform highp vec3 cameraPositionRelativeToModel;
+uniform highp vec4 colorIndex[256];
+uniform highp int color8Bit;
+
+const float maxDist = sqrt(2.0);
+const int sampleCount = 1024;
+const float alphaThreshold = 0.001;
+void main() {
+    // Raytrace into volume, need to sample pixels along the eye ray until we hit opacity 1
+
+    // Find out where ray intersects the object
+    highp vec3 rayDir = -(cameraPositionRelativeToModel - pos);
+    highp vec3 invRayDir = 1.0 / rayDir;
+    highp vec3 minCorner = vec3(-1.0);
+    highp vec3 maxCorner = vec3(1.0);
+    highp vec3 t1 = invRayDir * (minCorner - pos);
+    highp vec3 t2 = invRayDir * (maxCorner - pos);
+    highp vec3 tmin = min(t1, t2);
+    highp vec3 tmax = max(t1, t2);
+    highp vec2 t = max(tmin.xx, tmin.yz);
+    t = min(tmax.xx, tmax.yz);
+    float tFar = min(t.x, t.y);
+    highp vec3 rayStart = pos;
+    // Flip Y and Z so QImage bits work directly for texture and first image is in the front
+    rayStart.yz = -rayStart.yz;
+    highp vec3 rayStop = pos + rayDir * tFar;
+    rayStop.yz = -rayStop.yz;
+
+    // Convert intersections to texture coords
+    rayStart = 0.5 * (rayStart + 1.0);
+    rayStop = 0.5 * (rayStop + 1.0);
+
+    highp vec3 curPos = rayStart;
+    highp float fullDist = distance(rayStop, rayStart);
+    highp float stepSize = maxDist / float(sampleCount); // TODO: Stepsize needs to be improved
+    highp vec3 step = normalize(rayStop - rayStart) * stepSize;
+    highp float totalDist = 0.0;
+    highp float totalAlpha = 0.0;
+    highp vec4 destColor = vec4(0, 0, 0, 0);
+    highp vec4 curColor = vec4(0, 0, 0, 0);
+    highp vec3 curRgb = vec3(0, 0, 0);
+    highp float curAlpha = 0.0;
+
+    for (int i = 0; i < sampleCount; i++) {
+        curColor = texture3D(textureSampler, curPos);
+        if (color8Bit != 0)
+            curColor = colorIndex[int(curColor.r * 255.0)];
+
+        curAlpha = curColor.a;
+        if (curAlpha > alphaThreshold) {
+            curRgb = curColor.rgb * curAlpha * (1.0 - totalAlpha);
+            destColor.rgb += curRgb;
+            totalAlpha += curAlpha;
+        }
+        curPos += step;
+        totalDist += stepSize;
+        if (totalDist > fullDist || totalAlpha >= 1.0) {
+            break;
+        }
+    }
+
+    destColor.a = totalAlpha;
+    gl_FragColor = clamp(destColor, 0.0, 1.0);
+}
+