Fix billboard error which used the wrong width for top and bottom width of...

Fix billboard error which used the wrong width for top and bottom width of trapezoid billboards. The reason is the use of cross-product, which flips the vertical axis used in calculations. Properly documented in the code now, API now works as expected. Bug and fix provided by pc0de.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@4030 dfc29bdd-3216-0410-991c-e03cc46cb475

source/Irrlicht/CBillboardSceneNode.cpp

@@ -84,6 +84,7 @@ void CBillboardSceneNode::render()
 	core::vector3df topHorizontal = horizontal * 0.5f * TopEdgeWidth;
 	horizontal *= 0.5f * Size.Width;
 
+	// pointing down!
 	core::vector3df vertical = horizontal.crossProduct(view);
 	vertical.normalize();
 	vertical *= 0.5f * Size.Height;
@@ -94,15 +95,15 @@ void CBillboardSceneNode::render()
 		vertices[i].Normal = view;
 
 	/* Vertices are:
-	3--0
-	| /|
-	|/ |
 	2--1
+	|\ |
+	| \|
+	3--0
 	*/
-	vertices[0].Pos = pos + topHorizontal + vertical;
-	vertices[1].Pos = pos + horizontal - vertical;
-	vertices[2].Pos = pos - horizontal - vertical;
-	vertices[3].Pos = pos - topHorizontal + vertical;
+	vertices[0].Pos = pos + horizontal + vertical;
+	vertices[1].Pos = pos + topHorizontal - vertical;
+	vertices[2].Pos = pos - topHorizontal - vertical;
+	vertices[3].Pos = pos - horizontal + vertical;
 
 	// draw
 

tests/billboards.cpp

@@ -5,8 +5,10 @@
 
 using namespace irr;
 
-// Test billboards
-bool billboards(void)
+namespace
+{
+// Test billboard sizing
+bool billboardSize(void)
 {
 	// Use EDT_BURNINGSVIDEO since it is not dependent on (e.g.) OpenGL driver versions.
 	IrrlichtDevice *device = createDevice(video::EDT_BURNINGSVIDEO, core::dimension2d<u32>(160, 120), 32);
@@ -106,3 +108,47 @@ bool billboards(void)
 
 	return result;
 }
+
+// Test billboard orientation
+bool billboardOrientation(void)
+{
+	// Use EDT_BURNINGSVIDEO since it is not dependent on (e.g.) OpenGL driver versions.
+	IrrlichtDevice *device = createDevice(video::EDT_BURNINGSVIDEO, core::dimension2d<u32>(160, 120), 32);
+	assert(device);
+	if (!device)
+		return false;
+
+	video::IVideoDriver* driver = device->getVideoDriver();
+	scene::ISceneManager * smgr = device->getSceneManager();
+
+	scene::ICameraSceneNode* cam = smgr->addCameraSceneNode();
+	scene::IBillboardSceneNode* bill = smgr->addBillboardSceneNode(0, core::dimension2df(40,40));
+	bill->setPosition(core::vector3df(0,-15,10));
+	bill->getMaterial(0).Lighting=false;
+	bill->getMaterial(0).setTexture(0, driver->getTexture("../media/fontcourier.bmp"));
+
+	bool result = false;
+
+	device->run();
+	driver->beginScene(true, true, video::SColor(255, 60, 60, 60));
+	smgr->drawAll();
+	driver->endScene();
+
+	result = takeScreenshotAndCompareAgainstReference(driver, "-billboardOrientation.png");
+
+	device->closeDevice();
+	device->run();
+	device->drop();
+
+	return result;
+}
+
+} // end anonymous namespace
+
+// Test billboards
+bool billboards(void)
+{
+	bool result = billboardSize();
+	result &= billboardOrientation();
+	return result;
+}