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ayatollah
Joined: 04 Sep 2005
Posts: 15
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 Posted: Wed Nov 23, 2005 10:15 am Post subject: Matrix Problems with rotating an object around its Pivot |
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I was wondering if somebody here could help me out?
I am trying to display a 3d Object (CAR) and want to move it forward. During this forward move, I want to rotate it's wheels around their own pivot point!
Everything works fine as long as the car does not move but once I start moving the car along it's Y axis, the wheels remain in place!
This is what I draw each frame:
| Code: |
static void draw_frame(float frame)
{
ScePspFVector3 eye, center, up;
sceGuStart(GU_DIRECT,list);
sceGuClear(GU_COLOR_BUFFER_BIT|GU_DEPTH_BUFFER_BIT);
sceGumPushMatrix();
sceGumLoadIdentity();
DrawCube(1.0f, frame);
sceGumPopMatrix();
sceGuFinish();
sceGuSync(0,0);
}
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and in the DrawCube, I have the following Commands:
| Code: |
void DrawCube(float scale, float frame)
{
ScePspFVector3 vec;
float angle;
ScePspFMatrix4 wheel;
ScePspFMatrix4 temp;
vec.x=scale, vec.y=scale, vec.z=scale;
sceGumScale(&vec);
sceGumDrawArray(GU_TRIANGLES,
GU_TEXTURE_32BITF|GU_NORMAL_32BITF|GU_VERTEX_32BITF|GU_INDEX_16BIT,
alight_NUMFACES*3, (void *)alight_idx, (void *)alight_vtx);
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.........
more faces are drawn here
........
and here I try my wheel thing (this displays one wheel and the RIM) and rotates it:
| Code: |
sceGumStoreMatrix(&temp);
sceGumLoadMatrix(&wheel);
sceGumLoadIdentity();
pos.trans.x = -lftire_pivot.px;
pos.trans.y = -lftire_pivot.py;
pos.trans.z = -lftire_pivot.pz;
sceGumTranslate(&pos.trans);
angle = frame*50 * (M_PI/180.0f);
sceGumRotateX(angle);
pos.trans.x = lftire_pivot.px;
pos.trans.y = lftire_pivot.py;
pos.trans.z = lftire_pivot.pz;
sceGumTranslate(&pos.trans);
sceGumDrawArray(GU_TRIANGLES,
GU_TEXTURE_32BITF|GU_NORMAL_32BITF|GU_VERTEX_32BITF|GU_INDEX_16BIT,
lftire_NUMFACES*3, (void *)lftire_idx, (void *)lftire_vtx);
sceGumDrawArray(GU_TRIANGLES,
GU_TEXTURE_32BITF|GU_NORMAL_32BITF|GU_VERTEX_32BITF|GU_INDEX_16BIT,
lfrim_NUMFACES*3, (void *)lfrim_idx, (void *)lfrim_vtx);
sceGumMultMatrix(&temp);
}
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lftire_pivot.px, lftire_pivot.py and lftire_pivot.pz hold the x, y and z of the wheel's Pivot Points. This rotates the wheel successfully on the NOT MOVING Car. However as soon as I put a translate on the very top of the drawcube, the car moves but the wheel remains on it's place..
My problem is, that I am fairly new to 3d and I dont really get the whole things with the matrices..
Thank you very much for your help. It's greatly appreciated!
Roland |
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ufoz
Joined: 10 Nov 2005
Posts: 86
Location: Tokyo
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| Posted: Wed Nov 23, 2005 11:03 am Post subject: |
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Instead of the
| Code: | sceGumStoreMatrix(&temp);
sceGumLoadMatrix(&wheel);
sceGumLoadIdentity(); |
at the start, try wrapping the wheel drawing in a
| Code: |
sceGumPushMatrix();
sceGumPopMatrix();
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pair, just like it's usually done in hierarchical transformations. |
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ayatollah
Joined: 04 Sep 2005
Posts: 15
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| Posted: Wed Nov 23, 2005 7:44 pm Post subject: |
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Thanx for the Hint... I will try that out tonight..
One thing:
How big is the Matrix Stack? How many matrices can I push there and get back out? |
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chp
Joined: 23 Jun 2004
Posts: 313
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| Posted: Thu Nov 24, 2005 12:02 am Post subject: |
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The matrix stack is currently 32 entries per type. There is currently no way of changing this at runtime, so if you need a bigger stack you have to change it yourself in gumInternal and recompile.
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GE Dominator |
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