# MRT support in iphone and deferred shading !

**URL:** <https://forums.imgtec.com/t/mrt-support-in-iphone-and-deferred-shading/1170>\
**Category:** PowerVR Insider\
**Created:** [August 25, 2011, 9:27am UTC](https://forums.imgtec.com/t/mrt-support-in-iphone-and-deferred-shading/1170 "2011-08-25T09:27:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![mkandula](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.imgtec.com/mkandula/32/123_2.png) [@mkandula](https://forums.imgtec.com/u/mkandula)\
**Post date:** [August 25, 2011, 9:27am UTC](https://forums.imgtec.com/t/mrt-support-in-iphone-and-deferred-shading/1170/1 "2011-08-25T09:27:18Z")

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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.

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**Author:** ![JoeDavis](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.imgtec.com/joedavis/32/71_2.png) [@JoeDavis](https://forums.imgtec.com/u/JoeDavis)\
**Post date:** [August 25, 2011, 10:06am UTC](https://forums.imgtec.com/t/mrt-support-in-iphone-and-deferred-shading/1170/2 "2011-08-25T10:06:27Z")

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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](https://www.imgtec.com/powervr/insider/powervr-sdk-docs.asp) for more information). There are currently no mechanisms exposed for directly accessing on chip memory.

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**Author:** ![stix](https://avatars.discourse-cdn.com/v4/letter/s/edb3f5/32.png) [@stix](https://forums.imgtec.com/u/stix)\
**Post date:** [September 15, 2011, 2:28pm UTC](https://forums.imgtec.com/t/mrt-support-in-iphone-and-deferred-shading/1170/3 "2011-09-15T14:28:46Z")

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On the NVidia Tegra devices you have MRT [http://www.khronos.org/registry/gles/extensions/NV/GL\_NV\_draw\_buffers.txt](http://www.khronos.org/registry/gles/extensions/NV/GL_NV_draw_buffers.txt)