I'm having bad rendering results with a bump map in Poser. Ther render on the left is Max and the same object in Poser gives this lousy result.

Not the blotchiness of the bump map. I'm using Poser 7. I don't seem to be having the same problem with other objects with similar bump maps. Only this one.

Any ideas as to why this is happening?

I've also posted this in the Max forum.

<strong>bandolin</strong><br />
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<p><em>Caution: just a hobbyist</em></p>

jeez, that really sux compared to max. try shading rate = 0.01.

I'd recommend turning the texture filtering on the bump map to none, as well.

JonTheCelt

Most likely causes are polygons with reversed normals or long thin triangles.

Will try all suggested. Thanks.

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<p><em>Caution: just a hobbyist</em></p>

I've seen that blotchiness before, especially in P7.  It seems to arise from too much negative bump.   

It looks to me like you've simply got the bump inverted.  You could try sticking
a math function node between the bump map and the mesh, to invert and
add a little at the same time.  Set the top input of the math function node to about 1.2,
and take the bottom input from the bump map image, then set to subtract.

If that's too far outward, decrease the number some.

What numerical value do you have in the Bump channel, and what units are you using in poser.

If you just tell me the number, I won't have a clue. Poser displays Bump and Displacement depths in your chosing display units. For example, .083 feet is actually one inch.

Anyway, if you instruct poser to simulate that bump map at a too-large scale it will look stupid. It's like you're trying to make the door cutouts several feet in depth, and that just doesn't work.

I suggest you change your Poser display units to inches, and then set the bump depth to something reasonable like .1 inch.

OK, I've set my display units to inches. The bump is now reading .96. Which I'm to assume is less than an inch.

<strong>bandolin</strong><br />
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<p><em>Caution: just a hobbyist</em></p>

I'd recommend turning the texture filtering on the bump map to none, as well.

What exactly does texture filtering do anyway?

<strong>bandolin</strong><br />
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Well, .96 inches is indeed less than one inch, but it is still 9.6 times what I suggested, which was .1 inch. Imagine you were doing a bump map for the wrinkles around a character's eyes which are typically only about .05 inches, but instead you used 10 times that, creating cracks half an inch deep. It wouldn't look right.

If you really want features that are significantly larger in depth than .1 inch, you should be using displacement not bump. Bump is primarily for effects that are very small in scale, often hundredths of an inch.

Texture filtering is a feature which helps avoid moiré patterns. A moiré pattern is an interference pattern that is very visually distrubing. It most often arises when two grid-like patterns are overlayed on each other.

In the case of computer graphics, it often occurs when you have a repeating texture (such as threads on a cloth or tiny stripes or a checkerboard pattern) which are then being viewed in such a way as the texture features are close to the size of individual pixels in your render, but not perfectly lined up with the pixels.

Texture filtering works by blurring the texture in proportion to how far away it is from the camera. It is slightly more complicated than that, but that's the basic idea.

I've attached an image demonstrating. There are three squares each loaded with a grid pattern I made in photoshop. The bottom one is facing the camera and is pretty close.

The upper squares are rotated parallel to the ground. The one on the left does not have texture filtering enabled and you can see places where the fine red lines (due to perspective) are skipped or doubled, depending on how they lined up with the rendered pixels. On the right, texture filtering is enabled, and most of the artifacts are minimized.

Texture filtering is useful not only for color, but for bump.

Here's another render of the same setup, from a different view point.