Hey guys,

I have this idea in my head for a render I'm wanting to do...I just can't decide which way would be better.

I need a broken mirror, like someone smashed their fist against it - and at first I figured it would work better as a model, but then started to wonder if a displacement map might not achive the same effect.

Anyone know if a displacement map would mess up the reflection of the figure? Or would I just be better off modeling myself a smashed mirror?

Here's a quick test using a stock 'broken glass' picture with colors inverted, plugged into Displacement node.   It should work with some fiddling... I think you may need to have a black surface just behind the mirror, then adjust the mirror and the surface so that the black shows in the cracks.

Maybe you could use the broken glass picture for the colors too. Use some math nodes to desaturate, optionally invert, and then clamp the picture, which will give you a pure black&white mask, and then use that mask to drive reflection strength, and an inverted version to drive diffuse color strengh.

just one question if I may as I am a novice

Should the broken glass photo have a black or white background

I attach a sample of a broken glass picture with a black backgroud

 

Thanks

 

Cool beans...I shall have to do some experimenting then.

Thanks guys. ^_^

The background color doesn't matter. You can always fix it with shader nodes.

For the displacement: you want inward displacement. You can use the photo as-is, connect it to the Displacement node and set the Displacement value to a negative number. The value should correspond with about half the thickness of the mirror glass.
This image would also be the right one to drive diffuse strength: just plug it straight into the Diffuse_Value input of the root node, at strength 1.000. Set the Diffuse Color to black.

To drive reflection strenght, you'd need a desaturated inverted version of this image. No problem: just add a Math->Math functions node to the material, set the function to Subtrackt, connect the image map to Value2 at strength 1, and you're done. Connect the output to Refraction_Value, keep the strength number as it is.

Hi !

here's an exemple !

...

I've use the original picture for more realism of the broken area ...

You know that the glass of the mirror actually has no diffuse color to speak of? That's why I suggested to drive the Diffuse_Value with the imagemap: the Diffuse_Value should be almost zero on the reflecting parts of the mirror, while it may be closer to 1 in the cracks.

Actually, the diffuse strength and the reflection strength added together should not exceed 1.0 for every point in the material. Driving the Diffuse_Value with the inverse of what drives Reflection_Value guarantees that this rule will be obeyed. You can connect Diffuse_Strength directly to the output of your Pow node.

That Pow node can be removed, by the way. You can plug the image map directly into the Subtract node, the Blender node and displacement value.

The screen of the tv is another exemple, i know a mirror dont have diffuse value ... And the pow make the texture in grey scale who is usefull for the displacement, the substract function make in greyscale but invert the color too ...