Merge pull request #91 from mlavik1/raymarching-improvements
Raymarching improvements
This commit is contained in:
Matias Lavik
GitHub
Коммит
0985225f74
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@ -68,12 +68,28 @@
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float4x4 _CrossSectionMatrix;
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#endif
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float3 getRayDir(frag_in fragIn)
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struct RayInfo
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{
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float3 startPos;
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float3 endPos;
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float3 direction;
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float2 aabbInters;
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};
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struct RaymarchInfo
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{
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RayInfo ray;
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int numSteps;
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float numStepsRecip;
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float stepSize;
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};
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float3 getViewRayDir(float3 vertexLocal)
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{
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if(unity_OrthoParams.w == 0)
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{
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// Perspective
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return normalize(ObjSpaceViewDir(float4(fragIn.vertexLocal, 0.0f)));
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return normalize(ObjSpaceViewDir(float4(vertexLocal, 0.0f)));
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}
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else
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{
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@ -84,6 +100,56 @@
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}
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}
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// Find ray intersection points with axis aligned bounding box
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float2 intersectAABB(float3 rayOrigin, float3 rayDir, float3 boxMin, float3 boxMax)
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{
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float3 tMin = (boxMin - rayOrigin) / rayDir;
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float3 tMax = (boxMax - rayOrigin) / rayDir;
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float3 t1 = min(tMin, tMax);
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float3 t2 = max(tMin, tMax);
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float tNear = max(max(t1.x, t1.y), t1.z);
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float tFar = min(min(t2.x, t2.y), t2.z);
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return float2(tNear, tFar);
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};
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// Get a ray for the specified fragment (back-to-front)
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RayInfo getRayBack2Front(float3 vertexLocal)
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{
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RayInfo ray;
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ray.direction = getViewRayDir(vertexLocal);
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ray.startPos = vertexLocal + float3(0.5f, 0.5f, 0.5f);
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// Find intersections with axis aligned boundinng box (the volume)
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ray.aabbInters = intersectAABB(ray.startPos, ray.direction, float3(0.0, 0.0, 0.0), float3(1.0f, 1.0f, 1.0));
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// Check if camera is inside AABB
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const float3 farPos = ray.startPos + ray.direction * ray.aabbInters.y - float3(0.5f, 0.5f, 0.5f);
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float4 clipPos = UnityObjectToClipPos(float4(farPos, 1.0f));
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ray.aabbInters += min(clipPos.w, 0.0);
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ray.endPos = ray.startPos + ray.direction * ray.aabbInters.y;
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return ray;
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}
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// Get a ray for the specified fragment (front-to-back)
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RayInfo getRayFront2Back(float3 vertexLocal)
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{
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RayInfo ray = getRayBack2Front(vertexLocal);
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ray.direction = -ray.direction;
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float3 tmp = ray.startPos;
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ray.startPos = ray.endPos;
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ray.endPos = tmp;
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return ray;
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}
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RaymarchInfo initRaymarch(RayInfo ray, int maxNumSteps)
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{
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RaymarchInfo raymarchInfo;
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raymarchInfo.stepSize = 1.732f/*greatest distance in box*/ / maxNumSteps;
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raymarchInfo.numSteps = (int)clamp(abs(ray.aabbInters.x - ray.aabbInters.y) / raymarchInfo.stepSize, 1, maxNumSteps);
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raymarchInfo.numStepsRecip = 1.0 / raymarchInfo.numSteps;
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return raymarchInfo;
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}
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// Gets the colour from a 1D Transfer Function (x = density)
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float4 getTF1DColour(float density)
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{
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@ -164,27 +230,24 @@
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}
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// Direct Volume Rendering
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frag_out frag_dvr (frag_in i)
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frag_out frag_dvr(frag_in i)
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{
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#define NUM_STEPS 512
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#define MAX_NUM_STEPS 512
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const float stepSize = 1.732f/*greatest distance in box*/ / NUM_STEPS;
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RayInfo ray = getRayBack2Front(i.vertexLocal);
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RaymarchInfo raymarchInfo = initRaymarch(ray, MAX_NUM_STEPS);
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float3 rayStartPos = i.vertexLocal + float3(0.5f, 0.5f, 0.5f);
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float3 lightDir = normalize(ObjSpaceViewDir(float4(float3(0.0f, 0.0f, 0.0f), 0.0f)));
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float3 rayDir = getRayDir(i);
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// Create a small random offset in order to remove artifacts
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rayStartPos = rayStartPos + (2.0f * rayDir / NUM_STEPS) * tex2D(_NoiseTex, float2(i.uv.x, i.uv.y)).r;
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ray.startPos += (2.0f * ray.direction * raymarchInfo.stepSize) * tex2D(_NoiseTex, float2(i.uv.x, i.uv.y)).r;
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float4 col = float4(0.0f, 0.0f, 0.0f, 0.0f);
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uint iDepth = 0;
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for (uint iStep = 0; iStep < NUM_STEPS; iStep++)
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float tDepth = 0.0;
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for (int iStep = 0; iStep < raymarchInfo.numSteps; iStep++)
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{
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const float t = iStep * stepSize;
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const float3 currPos = rayStartPos + rayDir * t;
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if (currPos.x < 0.0f || currPos.x >= 1.0f || currPos.y < 0.0f || currPos.y > 1.0f || currPos.z < 0.0f || currPos.z > 1.0f) // TODO: avoid branch?
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break;
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const float t = iStep * raymarchInfo.numStepsRecip;
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const float3 currPos = lerp(ray.startPos, ray.endPos, t);
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// Perform slice culling (cross section plane)
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#ifdef CUTOUT_ON
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@ -210,30 +273,26 @@
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// Apply lighting
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#ifdef LIGHTING_ON
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src.rgb = calculateLighting(src.rgb, normalize(gradient), lightDir, rayDir, 0.3f);
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src.rgb = calculateLighting(src.rgb, normalize(gradient), lightDir, ray.direction, 0.3f);
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#endif
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if (density < _MinVal || density > _MaxVal)
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src.a = 0.0f;
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// Optimisation: A branchless version of: if (density < _MinVal || density > _MaxVal) src.a = 0.0f;
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src.a *= step(_MinVal, density) * step(density, _MaxVal);
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col.rgb = src.a * src.rgb + (1.0f - src.a)*col.rgb;
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col.a = src.a + (1.0f - src.a)*col.a;
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if (src.a > 0.15f)
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iDepth = iStep;
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if (col.a > 1.0f)
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break;
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// Optimisation: A branchless version of: if (src.a > 0.15f) tDepth = t;
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tDepth = max(tDepth, t * step(0.15, src.a));
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}
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// Write fragment output
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frag_out output;
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output.colour = col;
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#if DEPTHWRITE_ON
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if (iDepth != 0)
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output.depth = localToDepth(rayStartPos + rayDir * (iDepth * stepSize) - float3(0.5f, 0.5f, 0.5f));
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else
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output.depth = 0;
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tDepth += (step(col.a, 0.0) * 1000.0); // Write large depth if no hit
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const float3 depthPos = lerp(ray.startPos, ray.endPos, tDepth) - float3(0.5f, 0.5f, 0.5f);
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output.depth = localToDepth(depthPos);
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#endif
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return output;
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}
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@ -241,36 +300,36 @@
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// Maximum Intensity Projection mode
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frag_out frag_mip(frag_in i)
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{
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#define NUM_STEPS 512
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const float stepSize = 1.732f/*greatest distance in box*/ / NUM_STEPS;
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#define MAX_NUM_STEPS 512
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float3 rayStartPos = i.vertexLocal + float3(0.5f, 0.5f, 0.5f);
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float3 rayDir = getRayDir(i);
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RayInfo ray = getRayBack2Front(i.vertexLocal);
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RaymarchInfo raymarchInfo = initRaymarch(ray, MAX_NUM_STEPS);
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float maxDensity = 0.0f;
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for (uint iStep = 0; iStep < NUM_STEPS; iStep++)
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float3 maxDensityPos = ray.startPos;
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for (int iStep = 0; iStep < raymarchInfo.numSteps; iStep++)
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{
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const float t = iStep * stepSize;
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const float3 currPos = rayStartPos + rayDir * t;
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// Stop when we are outside the box
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if (currPos.x < -0.0001f || currPos.x >= 1.0001f || currPos.y < -0.0001f || currPos.y > 1.0001f || currPos.z < -0.0001f || currPos.z > 1.0001f) // TODO: avoid branch?
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break;
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const float t = iStep * raymarchInfo.numStepsRecip;
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const float3 currPos = lerp(ray.startPos, ray.endPos, t);
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#ifdef CUTOUT_ON
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if (IsCutout(currPos))
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continue;
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#endif
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const float density = getDensity(currPos);
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if (density > _MinVal && density < _MaxVal)
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maxDensity = max(density, maxDensity);
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if (density > maxDensity && density > _MinVal && density < _MaxVal)
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{
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maxDensity = density;
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maxDensityPos = currPos;
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}
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}
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// Write fragment output
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frag_out output;
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output.colour = float4(1.0f, 1.0f, 1.0f, maxDensity); // maximum intensity
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#if DEPTHWRITE_ON
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output.depth = localToDepth(i.vertexLocal);
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output.depth = localToDepth(maxDensityPos - float3(0.5f, 0.5f, 0.5f));
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#endif
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return output;
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}
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@ -279,27 +338,20 @@
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// Draws the first point (closest to camera) with a density within the user-defined thresholds.
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frag_out frag_surf(frag_in i)
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{
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#define NUM_STEPS 1024
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const float stepSize = 1.732f/*greatest distance in box*/ / NUM_STEPS;
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#define MAX_NUM_STEPS 1024
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float3 rayStartPos = i.vertexLocal + float3(0.5f, 0.5f, 0.5f);
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float3 rayDir = getRayDir(i);
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// Start from the end, tand trace towards the vertex
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rayStartPos += rayDir * stepSize * NUM_STEPS;
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rayDir = -rayDir;
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RayInfo ray = getRayFront2Back(i.vertexLocal);
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RaymarchInfo raymarchInfo = initRaymarch(ray, MAX_NUM_STEPS);
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// Create a small random offset in order to remove artifacts
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rayStartPos = rayStartPos + (2.0f * rayDir / NUM_STEPS) * tex2D(_NoiseTex, float2(i.uv.x, i.uv.y)).r;
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ray.startPos = ray.startPos + (2.0f * ray.direction * raymarchInfo.stepSize) * tex2D(_NoiseTex, float2(i.uv.x, i.uv.y)).r;
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float4 col = float4(0,0,0,0);
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for (uint iStep = 0; iStep < NUM_STEPS; iStep++)
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for (int iStep = 0; iStep < raymarchInfo.numSteps; iStep++)
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{
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const float t = iStep * stepSize;
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const float3 currPos = rayStartPos + rayDir * t;
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// Make sure we are inside the box
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if (currPos.x < 0.0f || currPos.x >= 1.0f || currPos.y < 0.0f || currPos.y > 1.0f || currPos.z < 0.0f || currPos.z > 1.0f) // TODO: avoid branch?
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continue;
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const float t = iStep * raymarchInfo.numStepsRecip;
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const float3 currPos = lerp(ray.startPos, ray.endPos, t);
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#ifdef CUTOUT_ON
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if (IsCutout(currPos))
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continue;
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@ -310,7 +362,7 @@
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{
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float3 normal = normalize(getGradient(currPos));
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col = getTF1DColour(density);
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col.rgb = calculateLighting(col.rgb, normal, -rayDir, -rayDir, 0.15);
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col.rgb = calculateLighting(col.rgb, normal, -ray.direction, -ray.direction, 0.15);
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col.a = 1.0f;
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break;
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}
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@ -320,7 +372,9 @@
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frag_out output;
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output.colour = col;
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#if DEPTHWRITE_ON
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output.depth = localToDepth(rayStartPos + rayDir * (iStep * stepSize) - float3(0.5f, 0.5f, 0.5f));
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const float tDepth = iStep * raymarchInfo.numStepsRecip + (step(col.a, 0.0) * 1000.0); // Write large depth if no hit
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output.depth = localToDepth(lerp(ray.startPos, ray.endPos, tDepth) - float3(0.5f, 0.5f, 0.5f));
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#endif
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return output;
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}
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