Creating tracks in snow

Hi, firstly I’m quite new into panda3d.
I’m creating grader simulator program, in which the grader is supposed to clean road from snow.
So I have somehow to alter terrain (snow plane) when grader moves over it.

Firstly I tried with GeoMipTerrain and PNMImage. but it went terribly slow to update terrain from image with new tire tracks.

Then I found this video and tried to use shaders.

But even demomaster program gives me this error

:gobj(error): Cg program too complex for driver: /c/Users/.../demomaster-0.8/demo_nature/shaders/vertextexture2_new.sha.
 Try choosing a different profile.

And basic-shaders-only is turned off.

the same error comes when I add

float4 color = tex2Dlod(tex_0, float4( vtx_texcoord0, 0, 0));

to my vshader.

I’m using ATI HD5850 video card on windows 7.

Anyhow please guide me to right direction, so I could achieve my coal.

Simply put this in Config.prc:

basic-shaders-only #f

Tried that, but no changes. (I also mentioned it in my post)

Also starting demomaster as “ f f f” made no difference.
and if basic-shaders-only is enabled, demomaster will not show that demo at all and displays appropriate message about that setting being enabled.

Here is info about OpenGL:
GL version: 3.2.9232
GLU version:
Shading language version: 1.50
And Panda3D version is 1.6.2

Looks like your video card only support basic shader. What is your video card ?