Skipping triangles in a mesh

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#1

Hi,
I am drawing a mesh using a TRIANGLE_LIST. To draw the mesh I am looping over points.
To draw the TRIANGLE_LIST I have index and vertex buffers.
For example in the code below if I want to skip the triangles in point 5 and If I try with continue to skip this iteration in the loop in both vertex and index buffers I am getting a lot of graphics artefacts. What is the proper way of doing this?

batches_[0].geometry_->SetDrawRange(TRIANGLE_LIST, 0, (points_.Size() - 1), false);
float* dest = (float*)vertexBuffer_->Lock(0, (points_.Size() - 1), true);

// For each point draw triangles
for (unsigned i = 0; i < points_.Size(); ++i)
{

	if(i==5)
	{
		// Skip this point
		// This apporach has graphics artefacts
		continue;
	}

	// Draw triangles
	// Update dest

}
#2

Nah, your approach is too naiive.

You need to build-up triangles in index buffer, and vertex buffer and skip through whole triangle (3 index positions).

#3

I already have index and vertex buffer but I can’t update them properly during the loop. My question is how to do it properly?

#4

Take look at my Material Effects repo and see how VCol change happens. You could probably change a bit of that code for your needs.

Edit: hmm, that won’t do. Take a look at Geom-Replication repo for reference instead. What you should do is retain the original copy of your idxbuffer and make changes to that to skip triangle draws.

#5

I haven’t tested the performance to heavily on this piece of code, but here’s how I handle updating the Vertex/Index buffers. Essentially, I rebuild the vertex list… but again, not sure how much that will effect performance in the long run as it’s quick and dirty. I’ve only used it for low-poly objects. A method can easily be added to remove a face which will rebuild the vertexList when calling the Commit() method.

#6

Oh, also, just a note when updating the StaticMesh component. I’ve had to do the following

StaticModel* model = GetStaticModelComponent();
model->SetModel(null); // Clear out the previous model so this can get updated.
model->SetModel(YourUpdatedModel());

This is due to this line here (I’d like to know if this is correct however, as it doesn’t feel right)…: