I bought your behavior, your document write:
" If both group index values are the same and negative, don't collide" but when I set group index negative (-2) ,Its always return positive (2) and collide. Is it a bug?
Sorry,I read your document and play with "collision filter" for 5 hours but I can not understand how to combine together "Category bits", "Mask Bits" and "Group index" .Its really hard for me , so Do you have any example capx for "collision filter"? Thank you very much