Displaying 2D Backgrounds         How to display a background 2D image using Rectangle2D
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A frequently asked question is how to display a 2D background image in OGRE. Here is an example of how to achieve this using the Rectangle2D class. This also demonstrates e.g. how to easily scroll the background. 

// Create background material
MaterialPtr material = MaterialManager::getSingleton().create("Background", "General");
material->getTechnique(0)->getPass(0)->createTextureUnitState("rockwall.tga");
material->getTechnique(0)->getPass(0)->setDepthCheckEnabled(false);
material->getTechnique(0)->getPass(0)->setDepthWriteEnabled(false);
material->getTechnique(0)->getPass(0)->setLightingEnabled(false);
 
// Create background rectangle covering the whole screen
Rectangle2D* rect = new Rectangle2D(true);
rect->setCorners(-1.0, 1.0, 1.0, -1.0);
rect->setMaterial("Background");
 
// Render the background before everything else
rect->setRenderQueueGroup(RENDER_QUEUE_BACKGROUND);
 
// Hacky, but we need to set the bounding box to something big
// NOTE: If you are using Eihort (v1.4), please see the note below on setting the bounding box
rect->setBoundingBox(AxisAlignedBox(-100000.0*Vector3::UNIT_SCALE, 100000.0*Vector3::UNIT_SCALE));
 
// Attach background to the scene
SceneNode* node = mSceneMgr->getRootSceneNode()->createChildSceneNode("Background");
node->attachObject(rect);
 
// Example of background scrolling
material->getTechnique(0)->getPass(0)->getTextureUnitState(0)->setScrollAnimation(-0.25, 0.0);

Note: You cannot add the 2D Rectangle directly to the root scene node. It will not show up.

Note on bounding boxes (Ogre v1.4 or above): Bounding boxes can now be infinite, which means that an object with an infinite bounding box will always be visible. This is practical in connection with Rectangle2D and replaces the hack of setting the bounding box to something very big. Instead just do this when setting the bounding box: 

// Use infinite AAB to always stay visible
AxisAlignedBox aabInf;
aabInf.setInfinite();
rect->setBoundingBox(aabInf);

 
Here is the port to MOGRE: 

// Create background material
MaterialPtr material = MaterialManager.Singleton.Create("Background", "General");
material.GetTechnique(0).GetPass(0).CreateTextureUnitState("rockwall.tga");
material.GetTechnique(0).GetPass(0).DepthCheckEnabled = false;
material.GetTechnique(0).GetPass(0).DepthWriteEnabled = false;
material.GetTechnique(0).GetPass(0).LightingEnabled = false;
 
// Create background rectangle covering the whole screen
Rectangle2D rect = new Rectangle2D(true);
rect.SetCorners(-1.0f, 1.0f, 1.0f, -1.0f);
rect.SetMaterial("Background");
 
// Render the background before everything else
rect.RenderQueueGroup = (byte)RenderQueueGroupID.RENDER_QUEUE_BACKGROUND;
 
// Use infinite AAB to always stay visible
AxisAlignedBox aab = new AxisAlignedBox();
aab.SetInfinite();
rect.BoundingBox = aab;
 
// Attach background to the scene
SceneNode node = mSmgr.RootSceneNode.CreateChildSceneNode("Background");
node.AttachObject(rect);
 
// Example of background scrolling
material.GetTechnique(0).GetPass(0).GetTextureUnitState(0).SetScrollAnimation(-0.25f, 0.0f);

 

See also

Alias: Displaying_2D_Backgrounds

Contributors to this page: spacegaier3733 points  , JustBoo , jacmoe111451 points  and Beauty5965 points  .
Page last modified on Tuesday 09 of November, 2010 11:54:32 GMT by spacegaier3733 points .

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