View Full Version : BLUR???? why god? why?

12-08-2005, 12:24 AM
Can someone explain why rendering blury reflections takes so much time more than peefect ones?

Like i resort to bluring them in photoshop as it's ridiculous. Isn't blurry stuff meant to be easier to render as it dosn't need the detail, or just a bit longer to apply the filter to the material?

Sorry for the spelling i'm feeling kinda wierd. To clarify when you make a material and add reflection and add blur to it the render time goes up tremendously.

Just wondering if there is a technical reason for this or if it could be a fault.

12-08-2005, 12:30 AM
Technically, it requires a lot more calculation. :)

Have you upgraded to 9.5 yet? Blurry effects are many times faster than they were in previous versions.

12-08-2005, 11:20 AM
Take out a pencil and draw a straight line...

now use the pencil to draw a fuzzy line.

Computer isn't much different...;-)

12-08-2005, 11:36 AM
Take out a pencil and draw a straight line...

now use the pencil to draw a fuzzy line.

Computer isn't much different...;-)

Heh, well said :)

12-08-2005, 06:41 PM
Rather than blurring the reflection, I find adding a slight bump is faster.

12-08-2005, 06:49 PM
i find blurring to be faster, and you don't have to ramp up the aa to get a decent result with it either. but if it's too slow then reduce the samples.

basically (so you can get an idea of what's going on), blurry reflection/refractions are done by tracing a whole load of rays at different angles to the surface, then averaging the results (not that dissimilar from gi in many respects), this process means that it's having to render and calculate a lot more information.

Why do it this way rather than as a single blur in post? Well firstly it looks right as a surface curves around and gets more oblique to the camera, and secondly objects that are closer to your blurry surface become sharper and objets further away become more blurry giving a very nice realistic effect. That's not to say blurring in post doesn't have it's place either (i have a post blurring plugin somewhere that's nice and fast but frankly falls down when it comes to things like strong bump maps), it's just that it's not going to get you as good results as the real raytracing deal.

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12-08-2005, 06:50 PM
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