Add some clarifying comments about the intermediate formats.

diff --git a/effect_chain.h b/effect_chain.h
index 071f9ebe51b33b511facbba7d7c2a68d8c542863..bc7e259af7ab856be686fe9e579379830cd4d83d 100644 (file)
--- a/effect_chain.h
+++ b/effect_chain.h
@@ -303,12 +303,12 @@ public:
        // while retaining reasonable precision for typical image data. It will,
        // however, cause some gamut clipping if your colorspace is far from sRGB,
        // as it cannot represent values outside [0,1]. NOTE: If you construct
-       // a chain where you end up bouncing pixels in non-linear light this
-       // will not do the wrong thing. However, it's hard to see how this
-       // could happen in a non-contrived chain; few effects ever need texture
-       // bounce or resizing without also combining multiple pixels, which
-       // really needs linear light and thus triggers a conversion before the
-       // bounce.
+       // a chain where you end up bouncing pixels in non-linear light
+       // (gamma different from GAMMA_LINEAR), this will be the wrong thing.
+       // However, it's hard to see how this could happen in a non-contrived
+       // chain; few effects ever need texture bounce or resizing without also
+       // combining multiple pixels, which really needs linear light and thus
+       // triggers a conversion before the bounce.
        //
        // If you don't need alpha (or can do with very little of it), GL_RGB10_A2
        // is even better, as it has two more bits for each color component. There
@@ -318,7 +318,10 @@ public:
        // the sRGB curve, and reduces maximum error (in sRGB distance) by almost an
        // order of magnitude, well below what you can get from 8-bit true sRGB.
        // (Note that this strategy avoids the problem with bounced non-linear data
-       // above, since the square root is turned off in that case.)
+       // above, since the square root is turned off in that case.) However, texture
+       // filtering will happen on the transformed values, so if you have heavy
+       // downscaling or the likes (e.g. mipmaps), you could get subtly bad results.
+       // You'll need to see which of the two that works the best for you in practice.
        void set_intermediate_format(
                GLenum intermediate_format,
                FramebufferTransformation transformation = NO_FRAMEBUFFER_TRANSFORMATION)