how to convert world coordinates to screen coordinates - c++

Question

I am creating a game that will have 2d pictures inside a 3d world.
I originally started off by not caring about my images been stretched to a square while I learnt more about how game mechanics work... but it's now time to get my textures to display in the correct ratio and... size.
Just a side note, I have played with orthographic left hand projections but I noticed that you cannot do 3d in that... (I guess that makes sense... but I could be wrong, I tried it and when I rotated my image, it went all stretchy and weirdosss).
the nature of my game is as follows:
In the image it says -1.0 to 1.0... i'm not fussed if the coordinates are:
topleft = 0,0,0
bottom right = 1920, 1200, 0
But if that's the solution, then whatever... (p.s the game is not currently set up so that -1.0 and 1.0 is left and right of screen. infact i'm not sure how i'm going to make the screen edges the boundaries (but that's a question for another day)
Question:
The issue I am having is that my image for my player (2d) is 128 x 64 pixels. After world matrix multiplication (I think that's what it is) the vertices I put in scale my texture hugely... which makes sense but it looks butt ugly and I don't want to just whack a massive scaling matrix into the mix because it'll be difficult to work out how to make the texture 1:1 to my screen pixels (although maybe you will tell me it's actually how you do it but you need to do a clever formula to work out what the scaling should be).
But basically, I want the vertices to hold a 1:1 pixel size of my image, unstretched...
So I assume I need to convert my world coords to screen coords before outputting my textures and vertices??? I'm not sure how it works...
Anyways, here are my vertices.. you may notice what I've done:
struct VERTEX
{
float X, Y, Z;
//float R, G, B, A;
float NX, NY, NZ;
float U, V; // texture coordinates
};
const unsigned short SquareVertices::indices[ 6 ] = {
0, 1, 2, // side 1
2, 1, 3
};
const VERTEX SquareVertices::vertices[ 4 ] = {
//{ -1.0f, -1.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f }, // side 1
//{ 1.0f, -1.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f },
//{ -1.0f, 1.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f },
//{ 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f }
{ -64.0f, -32.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f }, // side 1
{ 64.0f, -32.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f },
{ -64.0f, 32.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f },
{ 64.0f, 64.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f }
};
(128 pixels / 2 = 64 ), ( 64 / 2 = 32 ) because the centre is 0.0... but what do I need to do to projections, world transdoobifications and what nots to get the worlds to screens?
My current setups look like this:
// called 1st
void Game::SetUpViewTransformations( )
{
XMVECTOR vecCamPosition = XMVectorSet( 0.0f, 0.0f, -20.0f, 0 );
XMVECTOR vecCamLookAt = XMVectorSet( 0, 0, 0, 0 );
XMVECTOR vecCamUp = XMVectorSet( 0, 1, 0, 0 );
matView = XMMatrixLookAtLH( vecCamPosition, vecCamLookAt, vecCamUp );
}
// called 2nd
void Game::SetUpMatProjection( )
{
matProjection = XMMatrixPerspectiveFovLH(
XMConvertToRadians( 45 ), // the field of view
windowWidth / windowHeight, // aspect ratio
1, // the near view-plane
100 ); // the far view-plan
}
and here is a sneaky look at my update and render methods:
// called 3rd
void Game::Update( )
{
world->Update();
worldRotation = XMMatrixRotationY( world->rotation );
player->Update( );
XMMATRIX matTranslate = XMMatrixTranslation( player->x, player->y, 0.0f );
//XMMATRIX matTranslate = XMMatrixTranslation( 0.0f, 0.0f, 1.0f );
matWorld[ 0 ] = matTranslate;
}
// called 4th
void Game::Render( )
{
// set our new render target object as the active render target
d3dDeviceContext->OMSetRenderTargets( 1, rendertarget.GetAddressOf( ), zbuffer.Get( ) );
// clear the back buffer to a deep blue
float color[ 4 ] = { 0.0f, 0.2f, 0.4f, 1.0f };
d3dDeviceContext->ClearRenderTargetView( rendertarget.Get( ), color );
d3dDeviceContext->ClearDepthStencilView( zbuffer.Get( ), D3D11_CLEAR_DEPTH, 1.0f, 0 ); // clear the depth buffer
CBUFFER cBuffer;
cBuffer.DiffuseVector = XMVectorSet( 0.0f, 0.0f, 1.0f, 0.0f );
cBuffer.DiffuseColor = XMVectorSet( 0.5f, 0.5f, 0.5f, 1.0f );
cBuffer.AmbientColor = XMVectorSet( 0.2f, 0.2f, 0.2f, 1.0f );
//cBuffer.Final = worldRotation * matWorld[ 0 ] * matView * matProjection;
cBuffer.Final = worldRotation * matWorld[ 0 ] * matView * matProjection;
cBuffer.Rotation = XMMatrixRotationY( world->rotation );
// calculate the view transformation
SetUpViewTransformations();
SetUpMatProjection( );
//matFinal[ 0 ] = matWorld[0] * matView * matProjection;
UINT stride = sizeof( VERTEX );
UINT offset = 0;
d3dDeviceContext->PSSetShaderResources( 0, 1, player->texture.GetAddressOf( ) ); // Set up texture
d3dDeviceContext->IASetVertexBuffers( 0, 1, player->vertexbuffer.GetAddressOf( ), &stride, &offset ); // Set up vertex buffer
d3dDeviceContext->IASetPrimitiveTopology( D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST ); // How the vertices be drawn
d3dDeviceContext->IASetIndexBuffer( player->indexbuffer.Get( ), DXGI_FORMAT_R16_UINT, 0 ); // Set up index buffer
d3dDeviceContext->UpdateSubresource( constantbuffer.Get( ), 0, 0, &cBuffer, 0, 0 ); // set the new values for the constant buffer
d3dDeviceContext->OMSetBlendState( blendstate.Get( ), 0, 0xffffffff ); // DONT FORGET IF YOU DISABLE THIS AND YOU WANT COLOUR, * BY Color.a!!!
d3dDeviceContext->DrawIndexed( ARRAYSIZE( player->indices ), 0, 0 ); // draw
swapchain->Present( 1, 0 );
}
Just to clarify, if I make my vertices use 2 and 1 respective of the fact my image is 128 x 64.. I get a normal looking size image.. and yet at 0,0,0 it's not at 1:1 size... wadduuuppp buddyyyy
{ -2.0f, -1.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f }, // side 1
{ 2.0f, -1.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f },
{ -2.0f, 1.0f, 0.0f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f },
{ 2.0f, 2.0f, 0.0f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f }
Desired outcome 2 teh max:
Cool picture isn't it :D ?
Comment help:

Answer 1

I'm not familliar with direct-x but as far as I can see the thing with your image that is screen coordinates are [-1...+1] on x and y. So total length on both axis equals 2 and your image is scaled times 2. Try consider this scale in camera matrix.