Imagination PowerVR SDK Blog

PVRTTriStrip not working even in a simple case.


#1

PVRTTriStrip didn’t seem to work and I generated a very easy problem to see if it finds a solution. I provided it with a 9 triangles which could be easily ordered in ONE triangle strip, but it suggested 9 triangle strips. The input index data is:



0, 1, 2, 1, 2, 3, 2, 3, 4, 3, 4, 5, 4, 5, 6, 5, 6, 7, 6, 7, 8, 7, 8, 9, 8, 9, 10



Am I missing something?


#2

Hi Ahmad,



Apologies for the delayed response. I hadn’t spotted it before as you’d posted in the “FlowCloud Developers” section of the forum. I’ve now moved the discussion to the “PowerVR Insider Graphics” section, as its related to PVRTools.



I believe the problem is caused by your winding order changing. When the PVRTTriStrip function parses your triangle list, it interprets each triangle with a different winding order as the start of a new triangle list. So, your list should instead be:



0,1,2,

1,3,2,

2,3,4,

3,5,4,

4,5,6,

5,7,6,

6,7,8,

7,9,8,

8 9,10



I’ve filed bug report BRN46851 for the function comment to be updated to clarify the required winding order.



Regards,

Joe


#3

Thanks Joe. Will check it out again.