DirectX 11 Vertices Coordinates

问题

I'm working on my first C++ and DirectX 11 project where my current goal is to draw a colored triangle on the screen. This has worked well without any problems. However, there's one part that I would like to change, but I don't know how. I've tried searching for a solution but I havn't found any yet, and I guess that the reason is because I don't really know what I should search for.

Currently I set up my triangles 3 vertices like this:

VertexPos vertices[] =
{
    { XMFLOAT3(  0.5f,  0.5f, 1.0f )},
    { XMFLOAT3(  0.5f, -0.5f, 1.0f )},
    { XMFLOAT3( -0.5f, -0.5f, 1.0f )},
}

Where VertexPos is defined like this:

struct VertexPos
{
    XMFLOAT3 pos;
};

Currenty, my vertices position is set up by the range -1.0F to 1.0F, where 0.0F is the center. How can I change this so that I can position my vertices by using "real" coordinates like this:

VertexPos vertices[] =
{
    { XMFLOAT3(  100.0f,  300.0f, 1.0f )},
    { XMFLOAT3(  200.0f,  200.0f, 1.0f )},
    { XMFLOAT3(  200.0f,  300.0f, 1.0f )},
}

回答1:

Usual way:
- create orthogonal projection matrix (XMMatrixOrthographicLH() if you using XMMATH)
- create constant buffer with this matrix on CPU side (C++ code) and on GPU size (vertex shader)
- multiply vertex positions by orthogonal projection matrix in vertex shader

Simpler way (from F.Luna book):

XMFLOAT3 SpriteBatch::PointToNdc(int x, int y, float z)
{
    XMFLOAT3 p;

    p.x = 2.0f*(float)x/mScreenWidth - 1.0f;
    p.y = 1.0f - 2.0f*(float)y/mScreenHeight;
    p.z = z;

    return p;
}

Almost the same, but on CPU side. Of course, you can move this code to shader too.

P.S. Probably your book/manual/tutorials will learn you about it a little later. So, you better trust it and flow step-by step.

Happy coding! =)

来源：https://stackoverflow.com/questions/19226156/directx-11-vertices-coordinates

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