Hardware Skinning

tobspr · December 28, 2015, 10:45am

Melan:

Many thanks rdb for your reply.

However, I am currently struggling to understand how to mix HW instancing and skinning in a VS.

Let’s say a (simplified) HW instancing VS shader section made as below:
[this is actually how my HW instancing works, with some culling to cope with the OmniBoundingVolume() applied to the model]
mat4 transform =  transpose(shader_transformmatrix[gl_InstanceID])
gl_Position = p3d_ModelViewProjectionMatrix * (p3d_Vertex * transform);
where shader_transformmatrix is an uniform filled through a task with the instanced nodepath transform matrices - nodepath.getMat()

How should I modify the HW skinning matrix calculation below:
mat4 matrix = p3d_TransformTable[transform_index.x] * transform_weight.x
              + p3d_TransformTable[transform_index.y] * transform_weight.y
              + p3d_TransformTable[transform_index.z] * transform_weight.z
              + p3d_TransformTable[transform_index.w] * transform_weight.w;
with any additional ‘transform’ matrix based upon gl_InstanceID? (I am probably wrong/not clear in my understanding of how HW skinning is working…)

Thanks again fo your help!

Just wondering, why aren’t you doing the transform directly, e.g.

gl_Position = p3d_ViewProjectionMatrix * transform * p3d_Vertex;

As rdb already mentioned, if you use instancing, all models will play the same animation. To support different animations, panda would have to support that first. To combine the instancing and hardware skinning, I guess you want something like that:

gl_Position = p3d_ViewProjectionMatrix * transform * matrix * p3d_Vertex;

whereas matrix is the transform matrix.

Keep in mind that if you use p3d_ModelViewProjectionMatrix, this also includes the base models transform, rotation, and scale. Most likely you don’t want that if you pass a custom transform, so you should use p3d_ViewProjectionMatrix.