Few more hints:
Make sure texture format is one of hardware accelerated for Vertex Fetch on
your gpu.
Make sure texture filtering options are supported as well.
Few months ago I tried to do the same to learn that these matters are very
delicate. I used NVIdia 7800 GTX. It had texture vertex fetch support only
for float luminance, float rgba formats and point filter only (sometimes it
worked with bilinear but sometimes texels were black)
I finally gave up. Ended up with render to texture image and modifying
vertices by CPU. Hope you will have more luck ;-)
Cheers,
Wojtek Lewandowski
----- Original Message -----
From: "Mike Weiblen" <[EMAIL PROTECTED]>
To: "osg users" <[email protected]>
Sent: Tuesday, May 01, 2007 4:11 AM
Subject: Re: [osg-users] Height map vertex shader
Hi,
Various thoughts:
What graphics card? Not all support vertex textures in hardware, and may
have
different capabilities when they do.
Check the InfoLog outputs from the compile and link, they may provide
hints (ATI
says when the shader forced a slow path.)
FYI texture2DLod is only necessary when using a mipmapped texture. Are
you?
That could also have a performance impact.
cheers
-- mew
Zach Deedler wrote:
Hi Paul,
Yes I could've been more descriptive. "renders horribly", like 1fps.
The
texture I'm using is 512x256. The draw time is 1128ms. I'm up to date
with
my drivers.
Zach
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Paul Speed
Sent: Sunday, April 29, 2007 21:29
To: osg users
Subject: Re: [osg-users] Height map vertex shader
Can you describe what you mean by "renders horribly"?
Perhaps that will provide a clue.
Is this just a flat shaded shape? I noticed you aren't
giving it texture or color or anything.
-Paul
Zach Deedler wrote:
Hello osg-users,
I'm trying to implement dynamic terrain displacement using
a shader.
I am trying to just edit a texture to cause the vertex
shader to look
at the texture, and modify the vertex displacement. But, when I
implemented it, it renders horribly. Anybody see what I
did wrong in my vertex shader?
uniform sampler2D heightMapSampler;
void main()
{
vec3 vertex;
gl_TexCoord[0] = gl_MultiTexCoord0;
vec4 heightMap = texture2D( heightMapSampler,
gl_MultiTexCoord0.st );
vertex.xy = gl_Vertex.xy;
//Add displacement to vertex.
vertex.z = gl_Vertex.z + heightMap.r;
gl_Position = gl_ModelViewProjectionMatrix * vec4(vertex,1.0); }
I have a feeling I'm supposed to be using texture2DLod in
the vertex
shader, or that this just isn't a viable way to do vertex
displacements.
Thanks.
--
Mike Weiblen -- Austin Texas USA -- http://mew.cx/
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