Re: [Algorithms] VIPM With T&L - what about roam

[Jim O. <j.o...@in...>]

> ...
> BUT, what about software transforms in situations where the split order is
> not known, i.e. VDPM or ROAM where polygons are denser towards the camera?
> you cant specify a range of verts for the software transform because it
> quite literally could be any of them. HT&L is fine because of the only
> transform indexed verts thing.
>
> Is there a solution to this?

You could stream just the used vertices into a 'dynamic' vertexbuffer (i.e.
one you are using with the DISCARDCONTENTS paradigm) before rendering each
frame. Something like this:

(pseudo code warnings apply)

---- 8< ----
void RenderDevice::Draw(Array<Vertex> &verts, Array<ushort> &indices) {

    struct VertInfo {
        bool isUsed;        // is this vertex used?
        short newIndex;    // new index of this vertex (after streaming).
    };

    static VertInfo vertInfos[/* max. nr. of verts */];
    static short newIndices[/* max. nr. of indices */];

        // Clear all vertex info structures.
    memset(vertInfos, 0, sizeof(VertInfo) * /* max. nr. of verts */);

        // Rebuild the vertex list, using *only* used vertices.
    for (short i = 0; i < indices.GetLength(), i++) {
            // Get current vertex index.
        index = indices[i];
            // Check if we're using this vertex already...
        if (vertInfos[index].isUsed == false) {
                // If not, mark this vertex as used and remember it's index.
            vertInfos[index].newIndex = i;
            vertInfos[index].isUsed    = true;
            newIndices[i] = i;
                // Write a vertex to our dynamic vertexbuffer
            mDynVB->WriteVertex(i, verts[index]);
        }
            // Remap index.
         newIndices[i] = verts[index].newIndex;
    }
        // Draw everything.
    Draw(mDynVB, newIndices, indices.GetLength());
}
---- 8< ----

It remains to be seen whether the above will actually speed up rendering,
but it could.

Jim Offerman
Innovade


The Atlantis Project
http://www.theatlantisproject.com