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List:       kde-commits
Subject:    playground/libs/kgllib/examples/spinninglogos
From:       Rivo Laks <rivolaks () hot ! ee>
Date:       2008-02-04 15:26:44
Message-ID: 1202138804.410266.32097.nullmailer () svn ! kde ! org
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SVN commit 770870 by rivol:

Add some comments here as well

 M  +13 -4     logos.cpp  


--- trunk/playground/libs/kgllib/examples/spinninglogos/logos.cpp #770869:770870
@@ -29,6 +29,8 @@
 using namespace Eigen;
 
 
+// Vertex and texcoord arrays for a logo. We'll create a Mesh object using
+// those arrays
 static Vector3f logoShapeVertices[] =
     { Vector3f(-1.0f, -1.0f, 0.0f), Vector3f( 1.0f, -1.0f, 0.0f),
       Vector3f( 1.0f,  1.0f, 0.0f), Vector3f(-1.0f,  1.0f, 0.0f) };
@@ -63,13 +65,14 @@
     if (!mKDELogoTex->isValid() || !mQtLogoTex->isValid()) {
         return setErrorText("Data couldn't be loaded");
     }
-    // We only draw logos once, so set a GL_CLAMP wrap mode for them
+    // We don't want the textures to repeat (tile), so set a GL_CLAMP wrap mode
+    //  for them.
     mKDELogoTex->setWrapMode(GL_CLAMP);
     mQtLogoTex->setWrapMode(GL_CLAMP);
 
-    // This cuts away surfaces that doesn't face us. This way we can render
-    //  both logos at the same place without worrying about them intersecting
-    //  with each other
+    // This cuts away surfaces that doesn't face the camera (called backfacing
+    //  surfaces). This way we can render both logos at the same place without
+    //  worrying about them intersecting with each other
     glEnable(GL_CULL_FACE);
 
     // Enable blending so that transparent parts of the logo blend with the background
@@ -79,12 +82,15 @@
     // Use yellow background
     setClearColor(Vector4f(1.0, 1.0, 0.0, 0.0));
 
+    // Create the logo meshes
     mKDELogoMesh = createLogo(mKDELogoTex);
     mQtLogoMesh = createLogo(mQtLogoTex);
 }
 
 Mesh* Logos::createLogo(Texture* tex)
 {
+    // Create new mesh, using the vertex and texcoord arrays defined at the
+    // beginning of the file.
     Mesh* logo = new Mesh();
     logo->setVertexCount(logoShapeVertexCount);
     logo->setVertices(logoShapeVertices);
@@ -118,13 +124,16 @@
 
 void Logos::renderLogo(KGLLib::Texture* tex)
 {
+    // This both enables texturing as well as binds the texture.
     tex->enable();
+    // Now render the logo
     glBegin(GL_QUADS);
         glTexCoord2f(0.0f, 0.0f); glVertex3f(-1, -1, 0);
         glTexCoord2f(1.0f, 0.0f); glVertex3f( 1, -1, 0);
         glTexCoord2f(1.0f, 1.0f); glVertex3f( 1,  1, 0);
         glTexCoord2f(0.0f, 1.0f); glVertex3f(-1,  1, 0);
     glEnd();
+    // And finally disable texturing.
     tex->disable();
 }
 
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