Imagination PowerVR SDK Blog

MRT support in iphone and deferred shading !


#1

Hi,

I was wondering if there is MRT support on iphone 3GS and up ? Has anyone tried any forms of deferred shading techniques (light pre pass etc) ?

Are there any specific numbers for iphone 3GS regarding fill-rate, cache sizes, shader clock speed ?

I am assuming that the iphone powervr is tile-based deferred architecture and if so if on chip memory can be accessed in the shader ?

Thanks.




#2

MRT’s are not supported in the current versions of OGLES. I have seen a number of developers manage to utilise deferred shading on the 3GS at interactive frame rates, but this can only be done by working within the APIs limitations (i.e. performing additional render passes).





We cannot discuss the capabilities of the GPU in the 3GS.





Yes, PowerVR is a TBDR architecture (see “SGX Architecture Guide for Developers” on our documentation page for more information). There are currently no mechanisms exposed for directly accessing on chip memory.


#3

On the NVidia Tegra devices you have MRT http://www.khronos.org/registry/gles/extensions/NV/GL_NV_draw_buffers.txt