Imagination PowerVR SDK Blog

moving particular mesh in scene



I'm using the IntroducingPOD demo from the OGL 1.1 SDK, one the iPhone, as a basis/template for a game I'm working on. The scene file stores a mesh that serves as the track/level, a camera, lighting, and for now a sphere (I plan to include various other objects to which my question applies as well).

I also have a vec4 array that stores a path, that camera is placed on a node in that path and looks at a node X nodes ahead (x depending on interpolation steps of the path). I simply update the vFrom and vTo of the camera to make it follow the path.

Now I'm trying to place an object on a certain node, in this case the target node. Basically a sphere to show the target the camera is looking at. I have that sphere in the same scene file. Its props are stored in "ring" and the title of the model is ZTargetSphere.

My question: where in renderscene (assuming it shouldn't be done in drawmesh) should I override the "position" (and also rotation later on) of a particular mesh?  I've been trying different things but I'm kinda looking for the proper thing to do as well. I guess I could get it to work with gltranslate if I store the mesh in the scene on 0,0,0 but I think I should change the model matrix/view instead.

for(int i = 0; i < (int)m_Scene.nNumMeshNode; ++i)
        SPODNode& Node = m_Scene.pNode;

        // Gets the node model matrix
        PVRTMat4 mWorld;
        m_Scene.GetWorldMatrix(mWorld, Node);
        const char  *sphereTitle;
        sphereTitle = "ZTargetSphere";
        int testi = strcmp(sphereTitle, Node.pszName);
        PVRTMat4 mModelView;
        if (testi==0) {
            //NSLog(@"loading ZTargetSphere");
            // glTranslatef(ring.position.x, ring.position.y, ring.position.z);
            mModelView = m_mView * mWorld;
        } else {
            // Multiply the view matrix by the model (mWorld) matrix to get the model-view matrix
            mModelView = m_mView * mWorld;

JMan2010-10-14 22:25:27


I just solved my problem. Besides flipping the y and the z… I was placing the target sphere way too close to the camera Embarrassed


Glad you spotted the problem. Please post again if you have further questions and if you want to tell us how you’re getting on with your projectSmile