multiple Render targets with back and front FBO?

martel · April 3, 2018, 2:37pm

Hi!

i am thninking about one optimization to mi render that they have two passes, but the rendering works how to if only have one pass.

its in first step when i compute all scene, i dont try making deferred shading. The case is that i can get optimize me render using an second step only for compute specific layer that i extract from first pass with MTR.
(yes, to like blur shadows noise)
but actually i need attach the second layer that is all FragColor from first step, and how i dont using deferred shading it makes little sense using one FBO color texture for this, (the specifict layer that i have interest of compute in Quad is a 8bits GLRED)

i asking me if its possible use the first layer directly in topFBO screen and the second in my MRT tarjet to compute in second pass.

Dark_Photon · April 4, 2018, 7:16pm

As a native English speaker, I’m having trouble deciphering what you’re trying to say here. I’ll give it a shot though.

Is this what you’re saying?

Fuzzy_Paraphrase:

[ul]
[li]I am thinking about an optimization to my renderer. [/li][li]The optimization has 2 render passes. [/li][li]But currently my renderer only has 1 render pass. [/li][li]In my current renderer, in the first step, I compute the entire scene. [/li][li]My current renderer does NOT use Deferred Shading. [/li][li]The case in my current renderer that I can optimize is to only use a 2nd pass to compute on a specific layer extracted from the 1st pass with multiple-render-targets (MRT). [/li][li]This technique would be something like blurring shadows, or applying noise. [/li][li]However, to do this, I need to attach the 2nd MRT layer (from FragColor) from the 1st pass. [/li][li]Since I am not using deferred shading, it makes little sense to use an entire FBO with only one color texture attachment for this. [/li][li]The specific layer (2nd layer from the 1st pass) that I am interested in passing to the 2nd pass is 8-bit RED (single channel). [/li][/ul]
My question is: Is it possible to use the 1st MRT layer (from the 1st pass) in rendering the scene FBO, and the 2nd MRT layer (from the 1st pass) to compute in the 2nd pass.

If so, the answer is “yes”.

In the 1st pass, just write the 2nd layer to a texture (by attaching it to one of the FBO’s color attachments), and then in the 2nd pass, bind that texture to a shader sampler as input.