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EMBM Code

OpenGL

Started by soconne Jul 4, 2004 at 3:13 PM 9 replies 2k views

Original Post

soconne

107

soconne

Jul 4, 2004 at 3:13 PM

I recently found this code on the net for doing EMBM rendering with OpenGL without the use of pixel or vertex shaders.. But it uses a few ATI specific texture combiners. I was wondering if anyone knows how to perform EMBM without using these types of extensions. Here's the code glActiveTexture(GL_TEXTURE0_ARB); glEnable(GL_TEXTURE_2D); envMap->setCurrent(); glActiveTexture(GL_TEXTURE1_ARB); glEnable(GL_TEXTURE_2D); baseTexture->setCurrent(); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE_ARB); glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB_ARB, GL_MODULATE); glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE0_RGB_ARB, GL_TEXTURE0_ARB); glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_RGB_ARB, GL_PRIMARY_COLOR_ARB); glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE1_RGB_ARB, GL_TEXTURE); glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_RGB_ARB, GL_PRIMARY_COLOR_ARB); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_OUTPUT_RGB_ATIX, GL_TEXTURE0_ARB); glActiveTexture(GL_TEXTURE2_ARB); glEnable(GL_TEXTURE_2D); bumpMap->setCurrent(); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE_ARB); glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB_ARB, GL_BUMP_ENVMAP_ATI); glTexEnvi(GL_TEXTURE_ENV, GL_BUMP_TARGET_ATI, GL_TEXTURE0_ARB); static float f = 0; f += 0.001f; float rotMatrix[4]; rotMatrix[0] = 0.01f; rotMatrix[1] = 0; rotMatrix[2] = 0; rotMatrix[3] = 0.01f; glTexBumpParameterfvATI(GL_BUMP_ROT_MATRIX_ATI, (float *) &rotMatrix); glBegin(GL_QUADS); glMultiTexCoord2f(GL_TEXTURE0_ARB,0.5,0); glMultiTexCoord2f(GL_TEXTURE1_ARB,0.5f * f,0); glMultiTexCoord2f(GL_TEXTURE2_ARB,2 * f,0); glVertex3fv((GLfloat *) &v[0]); glMultiTexCoord2f(GL_TEXTURE0_ARB,1,0.5); glMultiTexCoord2f(GL_TEXTURE1_ARB,0.5f * f+1,0); glMultiTexCoord2f(GL_TEXTURE2_ARB,2 * f+2,0); glVertex3fv((GLfloat *) &v[1]); glMultiTexCoord2f(GL_TEXTURE0_ARB,0.5,1); glMultiTexCoord2f(GL_TEXTURE1_ARB,0.5f * f+1,1); glMultiTexCoord2f(GL_TEXTURE2_ARB,2 * f+2,2); glVertex3fv((GLfloat *) &v[2]); glMultiTexCoord2f(GL_TEXTURE0_ARB,0,0.5); glMultiTexCoord2f(GL_TEXTURE1_ARB,0.5f * f,1); glMultiTexCoord2f(GL_TEXTURE2_ARB,2 * f,2); glVertex3fv((GLfloat *) &v[3]); glEnd(); } Basically all the code does is render a water plane with a texture being perturbed by the bump map and it looks really cool.

hplus0603

Mod

3,014

hplus0603

Jul 4, 2004 at 3:48 PM

EMBM was, basically, a hack, and as such, the OpenGL standards body didn't bother standardizing it. Thus, you can only do it using vendor-specific extensions.

soconne

Author

107

soconne

Jul 4, 2004 at 6:17 PM

Well that really stinks.

So is the only other way through pixel shaders? You can't get a similiar effect through anything else?

_DarkWIng_

Jul 5, 2004 at 2:34 AM

You can get it trough GL_NV_texture_shader(2,3) on GF3 and 4.

soconne

Author

107

soconne

Jul 5, 2004 at 11:26 AM

Well I have a Radeon 9800. I am making a game, and I'd like to have nice water in it and still support a range of graphics cards without the use of pixel shaders.

I remember seeing a demo from ATI a long time ago for their 7500 card I think, and they had EMBM in the demo. You think they were using ATI specific extensions even back then?

Ingenu

132

Ingenu

Jul 5, 2004 at 11:55 AM

EMBM = Environnement Mapped Bump Mapping, it does dot3 and lookup in a cube map, it's not an "hack", Emboss Bump Mapping or UV Bump Mapping are hacks.

_DarkWIng_

Jul 5, 2004 at 12:43 PM

Quote:
Original post by Ingenu
EMBM = Environnement Mapped Bump Mapping, it does dot3 and lookup in a cube map, it's not an "hack"

EMBM by itself is not a hack, but the way ATI implemented it is. Do you see a cubemap anywhere in his code. With GL_NV_texture_shader(1/2/3) you can do both, "hacked" and real verison. But it's a bit more work to do it (not directly exposed as on ATI).

vincoof

Jul 5, 2004 at 2:34 PM

Quote:
I remember seeing a demo from ATI a long time ago for their 7500 card I think, and they had EMBM in the demo. You think they were using ATI specific extensions even back then?

If the demo was running in front the OpenGL API, then yes.

Quote:
EMBM = Environnement Mapped Bump Mapping, it does dot3 and lookup in a cube map, it's not an "hack", Emboss Bump Mapping or UV Bump Mapping are hacks.

The meaning of EMBM as exposed by this extension is the meaning of DX6's BumpEnv. And this is a real hack. There is very little physical coherency in this model. Mark Kilgard demonstrated it in a paper discussing bump-mapping techniques. Even emboss bump mapping is a "better" (read as : "more realistic", physically speaking) model.

Ingenu

132

Ingenu

Jul 5, 2004 at 4:11 PM

I wasn't discussing this particular extension, but rather giving the definition of EMBM.
Whether people missname extension isn't of my responsability.
Things have names, and using the proper name for the proper thing and reciprocaly is a requirement to get understood.
That's all.

soconne

Author

107

soconne

Jul 5, 2004 at 5:12 PM

Sooo..........then is it possible to get the same water effect using Dot3 Bumpmapping and OpenGL :-)

vincoof

Jul 6, 2004 at 2:57 AM

Not really. The DOT3 capability itself is not enough. You also need texture-dependant read capability.
For instance, GeForce and GeForce2 can perform dot products but can't perform texture-dependant reads, so these graphics cards can't render EMBM.
Through vendor-specific extension, you can perform such lookups on a GeForce3 and up (not GeForce4MX though) thanks to the the aforementioned NV_texture_shader extensions, and on the ATi side you can use ATI_fragment_shader for Radeon8500 and up. And for GeForceFX (and up) and Radeon9500 (and up) you can use the ARB_fragment_shader extension (sometimes referred as 'pixel shaders').

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