Followers 0

DX11 Display Quad in top left corner.

4 posts in this topic

Hi there,
I am very new to rendering, and i have a problem displaying a quad on the top left corner of my screen.
I already have a small 3D engine, and i wanted to use this code http://www.rastertek.com/dx11tut22.html to display my quad.
The issue is that the quad shows, but way off the -x axis and up the y axis. So i actually have to move my camera down the -z axis and tilt it to the left to see the quad.

Camera position and aiming when starting :

After going way back and turning a on the left

I just want it to stick in front of my camera in the top left corner of my screen.
My guts tell me there is something wrong with my view matrix, or at least, it is not setup the way the rastertek tutorial expected it, but i can't find exactly what it is.

cbuffer PerFrameBuffer
{
float4x4 gWorldViewProj;
};

PixelInputType VS(VertexInputType input)
{
PixelInputType output;

// Change the position vector to be 4 units for proper matrix calculations.
input.position.w = 1.0f;

// Calculate the position of the vertex against the world, view, and projection matrices.
output.position = mul(float4(input.position.xyz, 1.0f), gWorldViewProj);

// Store the texture coordinates for the pixel shader.
output.tex = input.tex;

return output;
}


XMMATRIX worldViewProj = world * camera->View() * camera->Proj();
mTextureEffect->mfxWorldViewProj->SetMatrix(reinterpret_cast<float*>(&(worldViewProj)));


XMMATRIX Camera::View()const
{
}

void Camera::UpdateViewMatrix()
{

// Keep camera's axes orthogonal to each other and of unit length.
L = XMVector3Normalize(L);
U = XMVector3Normalize(XMVector3Cross(L, R));

// U, L already ortho-normal, so no need to normalize cross product.
R = XMVector3Cross(U, L);

// Fill in the view matrix entries.
float x = -XMVectorGetX(XMVector3Dot(P, R));
float y = -XMVectorGetX(XMVector3Dot(P, U));
float z = -XMVectorGetX(XMVector3Dot(P, L));

XMStoreFloat3(&mRight, R);
XMStoreFloat3(&mUp, U);
XMStoreFloat3(&mLook, L);

mView(0,0) = mRight.x;
mView(1,0) = mRight.y;
mView(2,0) = mRight.z;
mView(3,0) = x;

mView(0,1) = mUp.x;
mView(1,1) = mUp.y;
mView(2,1) = mUp.z;
mView(3,1) = y;

mView(0,2) = mLook.x;
mView(1,2) = mLook.y;
mView(2,2) = mLook.z;
mView(3,2) = z;

mView(0,3) = 0.0f;
mView(1,3) = 0.0f;
mView(2,3) = 0.0f;
mView(3,3) = 1.0f;
}


The shader output vertices with very big negative values, when my camera is almost centered at the world origin, so there is no way it can see those.
So i am a bit confused about how i am supposed to use the view transformation (if the problem indeed lies there) so i can always see my quad no matter where i look.
Any help or suggestion would be greatly appreciated :-)

Thanks !
0

Share on other sites

You don't really need view matrix to render 2D image on screen.

Try to take a look at this tutorial, which is specifically made to render 2D things on the screen, not 3D space.

It should explain how to position things on the screen, and you should be able to easily see where's your mistake.

Edited by Zaoshi Kaba
1

Share on other sites

You don't really need view matrix to render 2D image on screen.

Try to take a look at this tutorial, which is specifically made to render 2D things on the screen, not 3D space.

It should explain how to position things on the screen, and you should be able to easily see where's your mistake.

Thanks a lot for the reply !

I read that tutorial, and i have to admit i am still confused because i think this is extacly what i am doing.

But i kept diging into http://www.d3dcoder.net/d3d11.htm and i found a similar code in the shadowmap sample which works for me :

I just don't know why yet.

Contrary to rastertek code, the d3dcoder code creates vertices directly in NDC space

	// Load the vertex array with data.
vertices[0].position = XMFLOAT3(-1.0f, -1.0f, 0.0f);
vertices[0].texture = XMFLOAT2(0.0f, 0.0f);

vertices[1].position = XMFLOAT3(-1.0f, +1.0f, 0.0f);
vertices[1].texture = XMFLOAT2(1.0f, 1.0f);

vertices[2].position = XMFLOAT3(+1.0f, +1.0f, 0.0f);
vertices[2].texture = XMFLOAT2(0.0f, 1.0f);

vertices[3].position = XMFLOAT3(+1.0f, -1.0f, 0.0f);
vertices[3].texture = XMFLOAT2(0.0f, 0.0f);


and only sends this world transform matrix to the shader :

XMMATRIX world(
0.5f, 0.0f, 0.0f, 0.0f,
0.0f, 0.5f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.5f, -0.5f, 0.0f, 1.0f);


Nothing else.

No projection or view matrix sent at all. And no matter where i look, the quad remains visible.

Its like the quad is not part of the rest of the "world" and "bypassed" the whole 3d part.

How is this possible ?

0

Share on other sites

Its like the quad is not part of the rest of the "world" and "bypassed" the whole 3d part.

How is this possible ?

Its just how graphics work. Your GPU does not know nor care what a view, projection matrix is, or whats drawn 3d and what not. It just sees vertices, and performs transformations on those in the vertex shader. You could even display a quad from (-1, -1, 0) to (1, 1, 0) without any transformation applied. What that matrix you supplied here does is scale the quad to 50% of its size, and move it 0.5 to the right, and 0.5 down. You don't need anything else, try to replace that matrix with identity and see what happens.

2

Share on other sites

Every vertices in the frustrum ends up being projected on the screen, and my screen surface IS the NDC space, ranging from -1 to 1.

So the whole point of world * view * proj operation is to convert my vertex from its 3D position to a 2D position in the NDC space.
And nothing stops me from sending vertices with NDC coordinates directly to the GPU.
I feel very stupid for realizing this only now... The whole thing makes sense now !

Thank you very much :-)

Note: Please do not hesitate to correct me if i came to a wrong conclusion, i would much rather know it now ;-)

0

Create an account

Register a new account

Followers 0

• Similar Content

• By YixunLiu
Hi,
I have a surface mesh and I want to use a cone to cut a hole on the surface mesh.
Anybody know a fast method to calculate the intersected boundary of these two geometries?

Thanks.

YL

• By hiya83
Hi, I tried searching for this but either I failed or couldn't find anything. I know there's D11/D12 interop and there are extensions for GL/D11 (though not very efficient). I was wondering if there's any Vulkan/D11 or Vulkan/D12 interop?
Thanks!

• Hi Guys,
I am just wondering if it is possible to acquire the address of the backbuffer if an API (based on DX11) only exposes the 'device' and 'context' pointers?
Any advice would be greatly appreciated

• bool InitDirect3D::Init() { if (!D3DApp::Init()) { return false; } //Additional Initialization //Disable Alt+Enter Fullscreen Toggle shortkey IDXGIFactory* factory; CreateDXGIFactory(__uuidof(IDXGIFactory), reinterpret_cast<void**>(&factory)); factory->MakeWindowAssociation(mhWindow, DXGI_MWA_NO_WINDOW_CHANGES); factory->Release(); return true; }
As stated on the title and displayed on the code above, regardless of it Alt+Enter still takes effect...
I recall something from the book during the swapChain creation, where in order to create it one has to use the same factory used to create the ID3D11Device, therefore I tested and indeed using that same factory indeed it work.
How is that one particular factory related to my window and how come the MakeWindowAssociation won't take effect with a newly created factory?
Also what's even the point of being able to create this Factories if they won't work,?(except from that one associated with the ID3D11Device)
• By ProfL
Can anyone recommend a wrapper for Direct3D 11 that is similarly simple to use as SFML? I don't need all the image formats etc. BUT I want a simple way to open a window, allocate a texture, buffer, shader.

• 12
• 28
• 14
• 11
• 34