color hash for geometry reuse is always 1

[muren400]

Hi,

when calling StreamingGeometryGenerator.hash in GeometryRunner, the color buffer's position is always set to the end of the buffer resulting in colors.hashCode() always returning 1.

BIMserver/BimServer/src/org/bimserver/geometry/GeometryRunner.java

Line 473 in 7f1661e

int hash = this.streamingGeometryGenerator.hash(indices, vertices, normals, colors);

The hash code of a byte buffer depends only upon its remaining elements; that is, upon the elements from position() up to, and including, the element at limit() - 1.

As a result, geometries can be reused if the mesh is identical although they have different index colors.

[muren400]

I created a pull request for this issue.

[hlg]

Yes, indeed. This issue seems to have been introduced in 126039c when changing from array to ByteBuffer for the geometry data. Yet, I was wondering why the buffer position seems to remain 0 for indices, vertices, normals and only the colors buffer is affected. I found that, apparently, only the colors ByteBuffer is exhausted when creating the color map:

BIMserver/BimServer/src/org/bimserver/geometry/GeometryRunner.java

Lines 358 to 361 in c06974e

	for (int i=0; i<colors.capacity(); i+=4) {
	colors.get(colorB);
	colorMap2.addColor(colorB);
	}

There is a comment on top of the StreamingGeometryGenerator.hash method saying "TODO add color??". I think this means that the author was not sure whether including color in the hash is a good idea. Ultimately they did and so I would restore this behaviour although it might be better in some cases to base reuse on geometry only and individually assign colors even to the reused geometries.