power vr

[Carter07]

(03-10-2013 11:35 PM)Henrik Wrote:  Ah, interesting I'm sure the problem is that PSP games forget to disable alpha test and draw lots of solid geometry with it on, as on PSP it doesn't cost anything, while it hurts us badly on PVR. So if we can detect for example when games are using fully opaque textures and no alpha in vertices, then we can disable the alpha test for that drawing. And maybe we can do more specific hacks for some games. It will be complicated but likely worth it for many mobile GPUs.

Ah so it's not possible to use Alpha Blend Mode instead?

I found this:

"It should also be noted that if a shader contains the ‘discard’ keyword then any object that shader
is applied to will suffer the cost of alpha test, even if the keyword is inside a conditional block that the
developer knows will not be hit for a draw call. The GPU cannot know the result of the conditional
without executing the fragment shader and so has to assume that the ‘discard’ keyword may be
hit. The solution to this is to move the use of ‘discard’ into a separate shader.
Under fixed function APIs it is essential that ‘alpha test’ be disabled for objects that do not require it.
It is common for ‘alpha test’ to be switched on at the beginning of a scene and left on for the entire
scene. This is strongly discouraged is it may severely harm performance.
The same visual effect as ‘discard’ can often be achieved through the use of the correct Alpha
Blend Mode, and setting the Alpha value to ‘0’ where ‘discard’ would be used.
If ‘discard’ or ‘alpha test’ cannot be avoided then objects using these techniques should be
submitted after all opaque geometry is submitted."

Hope something can be done because it's a worth opt for a lot of mobile phones since powervr are widely used , even apple users will like this when the jit works for them.