# DX11 Orthographic camera

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Hi Guys,

I am currently moving from DX9 (fixed function) to DX11. All is going well so far but now I am creating the camera system. But, my shader knowlegde is next to zero, so it is a bit different.

Primarily, I'll be making 2D applications (at this point in time) so I'll need an orthographic setup.

1 - Cheat and use dynamic vertex buffers and move everything manually.

2 - Setup a camera system.

Is #1 a valid one or is it purely a hack?

With #2 do I have to do this all with shaders or is there a way to do this with function calls? Could anyone point me in the right direction on how to go about this?

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#1: You could do it that way, but if you plan to do anything even moderately interesting with your camera, then you should consider option 2.

#2: It needs to be done in the shaders, as there is no fixed function pipeline anymore.  You can take a look at the old D3DX functions for inspiration in making the orthographic and view matrices though: D3DXMatrixOrthoLH and D3DXMatrixLookAtLH.

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I was fearing that might be the case.

I'll have to hit it head on and take up the challenge then.

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What Jason Z said.

Option 1 is how we did things before DirectX 7 introduced hardware TnL (transforms the vertices on the CPU every frame and send them through GPU, unviable past certain vertex count)

Option 2 (use shaders) is basically the same as Option 1 but the code runs on the GPU, hence no need to send the data every frame. It's already there.

Vertex Shaders are quite easy. Just think about it as a little program that gets executed for each vertex. One vertex in, one transformed vertex out (and each program execution can't see the contents of the other neighbouring vertices).

I've done both Options (option 1 a long, long time ago) and writting a vertex shader was just easier and quicker. Don't be scared of it just because you don't know it ;)

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What Jason Z said.

Option 1 is how we did things before DirectX 7 introduced hardware TnL (transforms the vertices on the CPU every frame and send them through GPU, unviable past certain vertex count)

Option 2 (use shaders) is basically the same as Option 1 but the code runs on the GPU, hence no need to send the data every frame. It's already there.

Vertex Shaders are quite easy. Just think about it as a little program that gets executed for each vertex. One vertex in, one transformed vertex out (and each program execution can't see the contents of the other neighbouring vertices).

I've done both Options (option 1 a long, long time ago) and writting a vertex shader was just easier and quicker. Don't be scared of it just because you don't know it ;)

Thanks Matias,

Just trying to sift through all of the information I can google right now.

Do you know of any good links for this subject (preferably just ortho if possible).

Thanks again.

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After a lot of reading and googling I now have this in my render loop.

 Totally changed from what I posted before

I think I am close now.

This is my render loop...

// Start Frame

float clearColor[4]={0.5f,0.5f,1.0f,1.0f};
d3dContext->ClearRenderTargetView(d3dBackBufferTarget,clearColor);

// tell DX11 to use this shader for the next renderable object
d3dContext->PSSetSamplers(0,1,&colorMapSampler);

// Set up the view
XMMATRIX viewMatrix=XMMatrixIdentity();
XMMATRIX projMatrix=XMMatrixOrthographicOffCenterLH(0.0f,(float)width,0.0f,(float)height,0.0f,100.0f);	// 800 x 600
viewMatrix=XMMatrixTranspose(viewMatrix);		// What is this for?
projMatrix=XMMatrixTranspose(projMatrix);		// What is this for?

// position the object
XMMATRIX scaleMatrix=XMMatrixScaling(1.0f*256.0f,1.0f*256.0f,1.0f );	// use variables later
XMMATRIX translationMatrix=XMMatrixTranslation(0.0f,0.0f,0.0f);		// position at 0,0,0
XMMATRIX worldMat=scaleMatrix*translationMatrix;

d3dContext->VSSetConstantBuffers(0,1,&worldCB);
d3dContext->VSSetConstantBuffers(1,1,&worldCB);
d3dContext->VSSetConstantBuffers(2,1,&worldCB);

// Render Geometry
UINT stride = sizeof(VERTEX);
UINT offset = 0;
d3dContext->IASetInputLayout(pLayout);
d3dContext->IASetVertexBuffers(0,1,&pVBuffer,&stride,&offset);
d3dContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLESTRIP);

d3dContext->Draw(4,0);

Texture2D colorMap_ : register( t0 );
SamplerState colorSampler_ : register( s0 );

cbuffer cbChangesEveryFrame : register(b0)
{
matrix worldMatrix;
};

cbuffer cbNeverChanges : register(b1)
{
matrix viewMatrix;
};

cbuffer cbChangeOnResize : register(b2)
{
matrix projMatrix;
}

struct VS_Input
{
float4 pos  : POSITION;
float2 tex0 : TEXCOORD0;
};

struct PS_Input
{
float4 pos  : SV_POSITION;
float2 tex0 : TEXCOORD0;
};

{
PS_Input vsOut = ( PS_Input )0;

vsOut.pos=mul(vertex.pos,worldMatrix);
vsOut.pos=mul(vsOut.pos,viewMatrix);
vsOut.pos=mul(vsOut.pos,projMatrix);

// vsOut.pos = vertex.pos;
vsOut.tex0 = vertex.tex0;

return vsOut;
}

float4 PShader( PS_Input frag ) : SV_TARGET
{
return colorMap_.Sample( colorSampler_, frag.tex0 );
}

The problem that I have not is that when I run the code I get an exception and the debug window reports this

ID3D11DeviceContext::UpdateSubresource: First parameter is corrupt or NULL [ MISCELLANEOUS CORRUPTION #13: CORRUPTED_PARAMETER1]

Which relates to this code...

d3dContext->UpdateSubresource(worldCB,0,0,&worldMat,0,0);
d3dContext->UpdateSubresource(projCB,0,0,&projMatrix,0,0);

Am I on the right track with how I am going about this? And any help as to what this error is would be awesome

Edited by DarkRonin

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A quick update.

I didn't realise I had to create the buffers so I added this before the render loop.

	ID3D11Buffer* viewCB=0;
ID3D11Buffer* projCB=0;
ID3D11Buffer* worldCB=0;

D3D11_BUFFER_DESC constDesc;
ZeroMemory(&constDesc,sizeof(constDesc));
constDesc.BindFlags=D3D11_BIND_CONSTANT_BUFFER;
constDesc.ByteWidth=sizeof(XMMATRIX);
constDesc.Usage=D3D11_USAGE_DEFAULT;

if(FAILED(d3dDevice->CreateBuffer(&constDesc,0,&viewCB)))
return 1;

if(FAILED(d3dDevice->CreateBuffer(&constDesc,0,&projCB)))
return 2;

if(FAILED(d3dDevice->CreateBuffer(&constDesc,0,&worldCB)))
return 3;

Things are better now, but the render results are not as expected. Hard to describe at the moment.

So, I'll play with the code a bit more to get my head around what is going on.

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This is what I get if I attempt to translate the sprite to 1,0 (supposedly in pixel co-ordinates). I also had to change the scale back to 1 (instead of 256 - the sprite width & height).

XMMATRIX scaleMatrix=XMMatrixScaling(1.0f,1.0f,1.0f );  // scale 256 was giving a black screen as something wrong here
XMMATRIX translationMatrix=XMMatrixTranslation(1.0f,0.0f,0.0f); // position at 1,0,0 
I am a lot closer than I was this morning. So, I am pretty happy that something is now happening. But, I am unsure whether the problem is in the shader or the code (both in a previous post).

XMMATRIX projMatrix=XMMatrixOrthographicOffCenterLH(0.0f,(float)width,0.0f,(float)height,0.0f,100.0f);


...doesn't seem to make any effect at all.

This is what I am seeing when translation is 1,0,0

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looks like you have your matrix multiplication reversed.

A * B * C != C * B * A

reverse the order.

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looks like you have your matrix multiplication reversed.

A * B * C != C * B * A

reverse the order.

In the shader do you mean?

I just tried reversing it and it gave the same result

One thing I did notice in my code I had...

d3dContext->VSSetConstantBuffers(0,1,&worldCB);
d3dContext->VSSetConstantBuffers(1,1,&worldCB);
d3dContext->VSSetConstantBuffers(2,1,&worldCB);

So, I have changed that to...

d3dContext->VSSetConstantBuffers(0,1,&worldCB);
d3dContext->VSSetConstantBuffers(1,1,&viewCB);
d3dContext->VSSetConstantBuffers(2,1,&projCB);


But now I get a blank screen.

Is the way I am setting the constant buffers correct?

[edit 2]
Actually the scaling had to be re-adjusted as a result (so I added the 256 multiplication back in where I took out before).

So, we are even closer.

This is the current result...

...which is closer to what I'd expect to see. But, it looks like the 0 on the y-axis is on the bottom of the screen instead of the top (probably something with my ortho setup) and I am getting an unwanted skew.

But, still on the right track I think.

Thanks for the help so far too guys

Edited by DarkRonin

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