Depth data using RTT

[natepak]

Hello,

I'm trying to create a program that will render the depth data to a texture. This is not for shadow mapping, so I need a texture independent of Ogre's shadow functions.

I can create the render texture, but I don't know how to tell Ogre to render depth data to it.

I create the render texture like so:
renderTexture = Ogre::TextureManager::getSingleton().createManual(
"myDepthTextureName",
Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME,
Ogre::TEX_TYPE_2D,
imageWidth, imageHeight, 0,
Ogre::PF_FLOAT16_R,
Ogre::TU_RENDERTARGET);

renderTaget = renderTexture[0]->getBuffer()->getRenderTarget();

I create a camera for the texture:
sceneMgr->createCamera("depthCameraName"); renderTarget->addViewport(camera);


I create a material:
Ogre::MaterialPtr matPtr = Ogre::MaterialManager::getSingleton().create(
"depthMatName", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);
matPtr->getTechnique(0)->getPass(0)->setLightingEnabled(false);
matPtr->getTechnique(0)->getPass(0)->createTextureUnitState("myDepthTextureName");

Does anyone know how to proceed from here? I can't figure out how to get Ogre to put depth (z-buffer) data into the texture instead of color data.

Thanks for the help.

[Assaf Raman]

Use a shader that color by the depth - and you will get the result you want.
Check out the "Depth of Field.rfx" sample in RenderMonkey (look the Depth sub project).

[natepak]

I've tried attaching a vertex and fragment shader that will compute the depth, but all I can get is a white screen.

Here is my vertex shader:

uniform mat4 worldViewProj;
uniform vec4 texelOffsets;
varying vec2 depth;

void main()
{
gl_Position = ftransform();

// fix pixel / texel alignment
gl_Position.xy += texelOffsets.zw * gl_Position.w;

depth.x = gl_Position.z;
depth.y = gl_Position.w;
}


Here is my frag shader:
varying vec2 depth;

void main()
{
float finalDepth = depth.x / depth.y;

// just smear across all components
// therefore this one needs high individual channel precision
gl_FragColor = vec4(finalDepth, finalDepth, finalDepth, 1);
}


This code was taken from the DepthShadowmap example in the ogre sources. Can someone notice what is wrong with the shaders?

Thanks,
-nate

[SpaceDude]

Assuming you are new to shaders, first thing to do is check that it's compiling correctly. Check you ogre.log to see if there are any errors.

Secondly, I would guess your values have a range greater than 1. When you save that to a texture or view it on screen all the values higher than 1 get clamped to 1. Likewise values lower than 0 get clamped to 0. Just to check your shader is working I would suggest you try the following line:

gl_FragColor = vec4(0.5, 0.5, 0.5, 1);

You should see a grey screen. If not, try to get that working first, then you can start worrying about your depth map.

[cyanbeck]

Hi, natepak,

you could take a look at this thread:
How to render the Z-buffer to a Texture