How to rotate a billboard, still facing to the camera?

[Clash]

Hello!

I want to rotate a billboard, but still make it look to the camera, like this:
Before Rotation:

Code: Select all

 _
|_|

After Rotation:

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/\
\/

I've used the search and they say a billboard can't be rotated, it should aways face the camera, but it will still be facing the camera!

If this is not possible, what kind of thing can I use to rotate stuff that should look 2D? I'm making a 2D Game

Thanks!

[arras]

Make custom node (look at custom node example). You can duplicate billboard scene node code. Only thing you have to change is position of vertices.

[rogerborg]

Code: Select all

#include <irrlicht.h>
using namespace irr;
using namespace core;
using namespace scene;
using namespace video;
using namespace io;
using namespace gui;

#ifdef _IRR_WINDOWS_
#pragma comment(lib, "Irrlicht.lib")
#endif

int main()
{
	IrrlichtDevice * device =
		createDevice( video::EDT_SOFTWARE, dimension2d<s32>(640, 480), 16,
			false, false, false, 0);
	IVideoDriver * driver = device->getVideoDriver();
	ISceneManager * smgr = device->getSceneManager();
	IGUIEnvironment * guienv = device->getGUIEnvironment();

	// Create a simple quad mesh
	SMeshBuffer * buffer = new SMeshBuffer();
	S3DVertex vertices[4];
	vertices[0] = S3DVertex(1.0f, 1.0f, 0.0f, 0.0f, 0.0f, -1.0f, SColor(0, 255, 255, 255), 1.0f, 1.0f);
	vertices[1] = S3DVertex(1.0f, -1.0f, 0.0f, 0.0f, 0.0f, -1.0f, SColor(0, 255, 255, 255), 1.0f, 0.0f);
	vertices[2] = S3DVertex(-1.0f, -1.0f, 0.0f, 0.0f, 0.0f, -1.0f, SColor(0, 255, 255, 255), 0.0f, 0.0f);
	vertices[3] = S3DVertex(-1.0f, 1.0f, 0.0f, 0.0f, 0.0f, -1.0f, SColor(0, 255, 255, 255), 0.0f, 1.0f);
	u16 indices[6] = { 0, 1, 2, 0, 2, 3 };
	buffer->append(vertices, 4, indices, 6);

	SMesh * mesh = new SMesh();
	mesh->addMeshBuffer(buffer);
	buffer->drop();
	// That's our quad mesh created

	// Create 3 mesh nodes that use it.
	IMeshSceneNode * nodes[3];
	
	for(int node = 0; node < 3; ++node)
	{
		nodes[node] = smgr->addMeshSceneNode(mesh);

		if (nodes[node])
		{
			nodes[node]->setMaterialFlag(EMF_LIGHTING, false);
			ITexture * texture = driver->getTexture("../../media/wall.bmp");
			nodes[node]->setMaterialTexture( 0, texture);
		}

		nodes[node]->setPosition(vector3df(node * 4.f, node * 3.f, 0.f));
	}
	mesh->drop();


	// Create an orthogonal (orthographic projection) camera
	ICameraSceneNode * camera = smgr->addCameraSceneNode(0, vector3df(0,0,-10), vector3df(0,0,0));
	matrix4 orthoMatrix;
	orthoMatrix.buildProjectionMatrixOrthoLH(20.f, 15.f, 5.f, 100.f);
	camera->setProjectionMatrix(orthoMatrix);
	camera->setIsOrthogonal(true);

	while(device->run())
	{
		driver->beginScene(true, true, SColor(255,100,101,140));

		// Rotate the 3 nodes at different rates
		for(int node = 0; node < 3; ++node)
		{
			vector3df rotation = nodes[node]->getRotation();
			rotation.Z += 0.1f * (node + 1); // Framerate dependent!
			nodes[node]->setRotation(rotation);
		}

		smgr->drawAll();
		driver->endScene();
	}

	device->drop();

	return 0;
}

[vitek]

rotation.Z += 0.1f * (node + 1); // Not framerate dependent!

What? I'm pretty the rotation rate is both frame rate dependent and index dependent. Say rotation.Z for node[0] is 0.f. If the render loop is executed 100 times per second, after 1 second, rotation.Z will be 100 * (.1f * 1) => 10.f. But if the loop runs at 10 frames per second, after 1 second, rotation.Z will be 10 * (.1f * 1) => 1.f. You can easily prove it to yourself by inserting device->sleep(250); in the end of the main loop.

And while I'm being a code nazi, I should mention that it might be a good idea to drop the mesh and buffer.

Travis

[rogerborg]

rotation.Z += 0.1f * (node + 1); // Not framerate dependent!

What? I'm pretty the rotation rate is both frame rate dependent and index dependent.

You make one little typo, and get sent to live with your auntie and uncle in Bel-Air.

And while I'm being a code nazi, I should mention that it might be a good idea to drop the mesh and buffer.

I haf obeyed ze orders, and fixed it.

[Clash]

Thanks a lot rogerborg, vitek and arras!

[GameCreator]

rogerborg, thanks a lot for the code!! I needed to do this as well.