Why do we use an index buffer instead of a vertex buffer?
Even more importantly, using an index buffer allows the adapter to store vertices in a vertex cache; if the primitive being drawn contains a recently-used vertex, that vertex can be fetched from the cache instead of reading it from the vertex buffer, which results in a big performance increase.
How to reorder data in a vertex buffer?
The solution to this problem is to use an index buffer. An index buffer is essentially an array of pointers into the vertex buffer. It allows you to reorder the vertex data, and reuse existing data for multiple vertices.
Why do you use an index buffer for triangles?
That makes sense because the two triangles share two common vertices. This duplicate data is wasteful, and the vertex buffer can be compressed by using an index buffer. A smaller vertex buffer reduces the amount of vertex data that has to be sent to the graphics adapter.
What should the vertex buffer look like in GPU?
If you bind the index buffer and tell the GPU to draw line segments connecting the vertices by the order specified in the indecies array: One can draw complexer figures without redefining the same vertices over and over again. This is the result: To achieve the same result without indices, the vertex buffer should look like the following:
Where are vertex and index data stored in Direct3D?
Vertex data is stored in vertex buffers, and index data is stored in index buffers. Listed below are a few common scenarios for drawing primitives using vertex and index buffers. These examples compare the use of IDirect3DDevice9::DrawPrimitive and IDirect3DDevice9::DrawIndexedPrimitive
How to draw a quad from a vertex buffer?
Let’s say you want to draw the quad that is shown in the following illustration. If you use the Triangle List primitive type to render the two triangles, each triangle will be stored as 3 individual vertices, resulting in a similar vertex buffer to the following illustration.