Displaying a depth texture?

I have a depth texture for shadowmapping that I want to draw on screen and debug. Is it enough just to do a conventional texture2D lookup to display the depth as an RGBA value, or do I have to do something special?

I believe so… IIRC depth textures are treated the same way as luminance textures.


Read the spec.

DEPTH_TEXTURE_MODE lets you draw the depth data as luminance, alpha, or intensity.

also u might wanna ampify the depth values as theyre most likely gonna be 0.99->1.0 + thus the texture will look white

eg something like
color = pow( depth_value, 100.0 );

draw a screen rectangle, then directly show it.

This is what I usually do if it’s just for debugging to get it into visible range. If you want to be more accurate though, you can compute the linear depth from the Z values.


And more, be careful about your near/far clip plane, maybe you will see a big white plane, scaled them to show gray level, much more clear.

Please forgive slight necro here…

I try using Humus’ equations to derive water depth for my shader, but just get black sea whatever I do… any tips at all?

You could try the match at the bottom of this thread (the Humus math does look OK tho):


Ah lol, it turns out that the built-in var gl_DepthRange isn’t being set properly for some reason (but containing a value which was neither higher, lower or equal to zero - presumably some sort of GLSL NAN value)!

Anyways… the equations are usable with my own hard-coded vals for near and far. I’m now seeing something whereby my water becomes more transparent as the camera distance increases:
Near: http://cid-25bcdd567f983189.skydrive.live.com/self.aspx/Public/water_low.PNG
Far: http://cid-25bcdd567f983189.skydrive.live.com/self.aspx/Public/water_high.PNG

I’m guessing this is a loss of accuracy in the depthVal as it moves away from the near plane. Would moving the near plane out as far as possible when rendering fix this maybe?

ed: if this is so, I presume I’m screwed when rendering beach scenes with near and far shallow water in it?!

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