rtcInterpolate0 with quad surfaces

Aguerre__Jose — Tue, 14 May 2019 15:35:35 GMT

Hi,

I am trying to get the color of a point inside a quad using rtcInterpolate0. I took the code from the "interpolation" example:

rtcSetGeometryVertexAttributeCount(quadGeom, 1);
rtcSetSharedGeometryBuffer(quadGeom, RTC_BUFFER_TYPE_VERTEX_ATTRIBUTE, 0, RTC_FORMAT_FLOAT3, vertices_color.data(), 0, sizeof(glm::vec3), vertices_color.size());

(.....)

glm::vec3 color(0.0f, 0.0f, 0.0f);
    unsigned int gID = query.hit.geomID;
               unsigned int pID = query.hit.primID;
               float u = query.hit.u;
               float v = query.hit.v;

               {
               rtcInterpolate0(rtcGetGeometry(eScene, gID), pID, u, v, RTC_BUFFER_TYPE_VERTEX_ATTRIBUTE, 0, &color.x, 3);
               }

The results I'm getting are correct, but I don't understand what are the u and v values supposed to represent. With triangles, I guess they are barycentric coordinates, but with quads these coordinates do not exist. Is embree dividing each quad into 2 triangles?

Thanks,

Jose

Hi Jose,

BenthinC_Intel — Tue, 14 May 2019 16:55:33 GMT

Hi Jose,

Embree is handling a quad as two triangles. Please have a look at the RTC_GEOMETRY_TYPE_QUAD section in the Embree documentation:

https://www.embree.org/api.html#rtc_geometry_type_quad

topic rtcInterpolate0 with quad surfaces in Intel® Embree Ray Tracing Kernels

rtcInterpolate0 with quad surfaces

Hi Jose,