access viewport pixel values in ogre

Question

I'm working on ogre project by using C++. Normally I use viewport:setbackground() but this cause whole window same colour. This time I want to load different R, G, B values for each viewport's pixel. My window is 600*600 and I have to load RGB values for each pixel. How can I solve this question ?

Answer 1

If you want to set a background you can do this:

Create a rectangle that fill all viewport

Rectangle2D* rect = new Rectangle2D(true);
rect->setCorners(-1.0, 1.0, 1.0, -1.0);
rect->setRenderQueueGroup(RENDER_QUEUE_BACKGROUND);
rect->setBoundingBox(AxisAlignedBox(-100000.0 * Vector3::UNIT_SCALE, 100000.0 * Vector3::UNIT_SCALE));
SceneNode * node = sceneManager->createChildSceneNode("Background");
node->attachObject(rect);

Create a material and texture

TexturePtr texture = TextureManager::getSingleton().createManual("BackgroundTex", ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME, TEX_TYPE_2D, 600, 600, 0, PF_R8G8B8, TU_DYNAMIC_WRITE_ONLY_DISCARDABLE);
MaterialPtr material = MaterialManager::getSingleton().create("BackgroundMat", ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);
Technique* technique = material->createTechnique();
technique->createPass();
technique->getPass(0)->setLightingEnabled(false);
technique->getPass(0)->createTextureUnitState("BackgroundTex");
rect->setMaterial("BackgroundMat");

Now you can copy your RGB data directly to texture framebuffer:

texture->getBuffer()->blitFromMemory(PixelBox(600, 600, 1, PF_R8G8B8, (void*) data));

EDIT 2011-11-10

data must be a valid pointer to a framebuffer of raw RGB. You can initialize it:

unsigned char* data = new unsigned char[600 * 600 * 3];

And than write yellow directly to pixel at position x,y.

unsigned char* red = &data[(x + y * width) * 3];
unsigned char* blue = &data[(x + y * width) * 3 + 1];
unsigned char* green = &data[(x + y * width) * 3 + 2];
*red = 255;
*blue = 0;
*green = 255;

Or write directly to texture->getBuffer() (Ogre API: HardwarePixelBuffer)

unsigned char* data = (unsigned char*)texture->getBuffer()->lock();

... write directly to pixelbuffer ...

texture->getBuffer()->unlock();

This example can be generalized for other width, length, format etc... You can use more optimized code to find pixel inside the buffer, this is just an example.