Fix winding issue in watertightness tests

The winding order of shared edge vertices wasn't consistent.
Add a check to ensure all triangles have same winding order.

Affects:
dEQP-VK.ray_tracing_pipeline.watertightness*
Components: Vulkan
VK-GL-CTS issue: 4009

Change-Id: I24607720fedcae2e903707dcd8f2d2d8b6ec12c0

diff --git a/external/vulkancts/modules/vulkan/ray_tracing/vktRayTracingWatertightnessTests.cpp b/external/vulkancts/modules/vulkan/ray_tracing/vktRayTracingWatertightnessTests.cpp
index 0ae3908..afd6224 100644 (file)
--- a/external/vulkancts/modules/vulkan/ray_tracing/vktRayTracingWatertightnessTests.cpp
+++ b/external/vulkancts/modules/vulkan/ray_tracing/vktRayTracingWatertightnessTests.cpp
@@ -104,6 +104,24 @@ namespace vkt
                                return result;
                        }
 
+                       static inline double doCrossProduct(tcu::DVec2 a, tcu::DVec2 b)
+                       {
+                               return a.x() * b.y() - a.y() * b.x();
+                       }
+
+                       static bool pointInTriangle2D(tcu::Vec3 p, tcu::Vec3 a, tcu::Vec3 b, tcu::Vec3 c)
+                       {
+                               tcu::DVec2 pa = { a.x() - p.x(), a.y() - p.y()} ;
+                               tcu::DVec2 pb = { b.x() - p.x(), b.y() - p.y()};
+                               tcu::DVec2 pc = { c.x() - p.x(), c.y() - p.y()};
+                               double v1 = doCrossProduct(pa, pb);
+                               double v2 = doCrossProduct(pb, pc);
+                               double v3 = doCrossProduct(pc, pa);
+
+                               // The winding of all the triangles in the test on XY plane is the same, so a negative value can be assumed
+                               return v1 < 0 && v2 < 0 && v3 < 0;
+                       }
+
                        deUint32 getShaderGroupSize(const InstanceInterface& vki,
                                const VkPhysicalDevice          physicalDevice)
                        {
@@ -445,6 +463,11 @@ namespace vkt
                                        const tcu::Vec3         mixed = mixVec3(mixVec3(a, b, alfa), c, beta);
                                        const float                     z = -rng.getFloat(0.01f, 0.99f);
                                        const tcu::Vec3         d = tcu::Vec3(mixed.x(), mixed.y(), z);
+
+                                       // A check to avoid vertices that are outside the triangle in the XY plane due to floating-point precision,
+                                       // resulting in inconsistent winding order
+                                       if(!pointInTriangle2D(d, a, b, c)) continue;
+
                                        const deUint32& p = t.x();
                                        const deUint32& q = t.y();
                                        deUint32& r = t.z();
@@ -453,7 +476,7 @@ namespace vkt
                                        vertices.push_back(d);
 
                                        triangles.push_back(tcu::UVec3(q, r, R));
-                                       triangles.push_back(tcu::UVec3(p, r, R));
+                                       triangles.push_back(tcu::UVec3(p, R, r));
                                        r = R;
                                }