using World transform to move objects stored on a single vertex buffer

Tubby94 · 2017-11-15T19:56:38

I'm currently learning how to store multiple objects in a single vertex buffer for efficiency reasons. So far I have a cube and pyramid rendered using ID3D12GraphicsCommandList::DrawIndexedInstanced; but when the screen is drawn, I can't see the pyramid because it is drawn inside the cube. I'm told to "Use the world transformation matrix so that the box and pyramid are disjoint in world space". Can anyone give insight on how this is accomplished? First I init the verts in Local Space std::array<VPosData, 13> vertices = { //Cube VPosData({ XMFLOAT3(-1.0f, -1.0f, -1.0f) }), VPosData({ XMFLOAT3(-1.0f, +1.0f, -1.0f) }), VPosData({ XMFLOAT3(+1.0f, +1.0f, -1.0f) }), VPosData({ XMFLOAT3(+1.0f, -1.0f, -1.0f) }), VPosData({ XMFLOAT3(-1.0f, -1.0f, +1.0f) }), VPosData({ XMFLOAT3(-1.0f, +1.0f, +1.0f) }), VPosData({ XMFLOAT3(+1.0f, +1.0f, +1.0f) }), VPosData({ XMFLOAT3(+1.0f, -1.0f, +1.0f) }), //Pyramid VPosData({ XMFLOAT3(-1.0f, -1.0f, -1.0f) }), VPosData({ XMFLOAT3(-1.0f, -1.0f, +1.0f) }), VPosData({ XMFLOAT3(+1.0f, -1.0f, -1.0f) }), VPosData({ XMFLOAT3(+1.0f, -1.0f, +1.0f) }), VPosData({ XMFLOAT3(0.0f, +1.0f, 0.0f) }) } Then data is stored into a container so sub meshes can be drawn individually SubmeshGeometry submesh; submesh.IndexCount = (UINT)indices.size(); submesh.StartIndexLocation = 0; submesh.BaseVertexLocation = 0; SubmeshGeometry pyramid; pyramid.IndexCount = (UINT)indices.size(); pyramid.StartIndexLocation = 36; pyramid.BaseVertexLocation = 8; mBoxGeo->DrawArgs["box"] = submesh; mBoxGeo->DrawArgs["pyramid"] = pyramid; Objects are drawn mCommandList->DrawIndexedInstanced( mBoxGeo->DrawArgs["box"].IndexCount, 1, 0, 0, 0); mCommandList->DrawIndexedInstanced( mBoxGeo->DrawArgs["pyramid"].IndexCount, 1, 36, 8, 0); Vertex Shader cbuffer cbPerObject : register(b0) { float4x4 gWorldViewProj; }; struct VertexIn { float3 PosL : POSITION; float4 Color : COLOR; }; struct VertexOut { float4 PosH : SV_POSITION; float4 Color : COLOR; }; VertexOut VS(VertexIn vin) { VertexOut vout; // Transform to homogeneous clip space. vout.PosH = mul(float4(vin.PosL, 1.0f), gWorldViewProj); // Just pass vertex color into the pixel shader. vout.Color = vin.Color; return vout; } float4 PS(VertexOut pin) : SV_Target { return pin.Color; }

Graphics and GPU Programming Programming DX12

Started by Tubby94 November 13, 2017 10:11 PM

10 comments, last by galop1n 7 years, 2 months ago

galop1n

1,046

November 15, 2017 07:56 PM

33 minutes ago, Tubby94 said:
I get that I can create new world and MVP matrices to separately describe the positions, but it still doesn't solve the problem of how I tell the shader to use MVPA on the cube and MVPB on the pyramid.

Because between the draw of the cube and the draw of the pyramid, you change the matrix to use, it is not a concern of the shader, it is a concern to change the constant buffer view to a different value ( and because you are doing DX12, deal with memory life time of buffer content ).

using World transform to move objects stored on a single vertex buffer

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