How to get sharp renders

[Crayox13]

Hi,
I have a scene where the client wants to see a lot of details in furniture, which is pretty flat, white color, and mittered edges. I stopped using catmull-rom a long time ago after I learned it was giving me edges on highlights, made transition between my scene, and the background weird, etc. So I was playing with a test scene and vray aa filters. They aren't really explained. I mean, there are 4, but no real explanation which one to use and when. Generally 2.0 will give you a nice render, above, it gets too blurry for my taste, but below, if I want details, it gets too rough around the edges. I use DMC, and even tried 8-20 subs, normally 4-8 is just fine for me, but still, the render is the same.

I'm attaching the render. How would I get all this edges to be "perfect"? Not blurry, but also, not aliased as in this. Here, I used vray Lanczcos 1.0

[glorybound]

have you tried an ambient occlusion pass, blending it in PS?

[joconnell]

The problem you are seeing here is nothing but a limitation of resolution - Since every image is just a grid of different coloured pixels what you're seeing here is the bottom and top lines of the windows being nearly horizontal - you're getting issues where the edge of the geometry runs halfway between two pixels in the final image - lots of the pixels are different percentages window geometry and background environment - vray is blending between the colours of these two objects to give the illusion of a continuous edge - if you had pure colour for each object you'd get a very stepped looking edge since a pixel is a uniform size and can only be a single colour value.

[Crayox13]

Ambient occlusion should be under render elements? I can't find it.

Joconnell, see how catmull-rom does it nicely, but it leaves blotches and weird edges, as usual. It's even worse if a scene is more complex with reflective materials. I was wondering how to achieve this with vray AA filters.

[stevegh]

What you are seeing here is actually caused by the extreme contrast between the outside of the window, which I'm sure has a very very high value, and the inside of the window which is clearly between 0.0 and 1.0 (floating point). You can enable sub-pixel mapping and clamp output in the color mapping roll-out, but obviously this is going to leave you with less control in post. I think you may also want to try different color mapping options such as Reinhard and Exponential to get rid of the nasties.

[insanetk]

I recommend trying the detail enhancement feature. It does brute force GI in areas that it decides is not detailed enough, basically. Also, the antialias filters that sharpen the image does not handle 32-bit floating point (HDR) data very well. It backfires a lot when the values between two contrasting pixels are sky-high thanks to the 32-bit floating point range (HDR)

[leehumphries]

Im not saying this is the correct method but for one i would click sub-pixel mapping and clamp output in colour mapping that should stop the black lines around the window edges.

The achieve sharp renders i usually use Catmull rom filter and DMC sampling..Increase the samples to Min 8 Max 20...This will make the render longer but should give you a sharper image. Also mentioned previously add ambient occlusion...

[MegaPixel]

I think another method is to turn Anti Aliasing off all together, and just let the sampler settings do the sharpening. But ya, a little bit of everything mentioned above needs to be tried as well.

[flino2004]

on top of everything above you can render it double the resolution that your client wants and scale down in photoshop.

[Sliver_Creations]

Or render a smooth/clean image in 3DS Max and add sharpness Photoshop using the old fashion way. This is usually a faster way than rendering a sharp image in 3DS Max. Catmull-rom is very slow and often gives "sharpness" in places were it doesn't belong.

[joconnell]

To be honest I don't know if there's a major benefit in doing this - it was discussed before and vlado mentioned you're not going to get higher quality out of it or any speed benefits.

What the catmull and other sharpening filter does is a colour correction wherever edges meet. If you've got a dark and a light edge meeting, it'll darken the row of pixels on the dark side and brighten the light ones to give them more contrast and thus more defined to your eye. On this page you can see a lot of different diagrams that show how this contrast is applied - http://www.blender.org/development/r...and-filtering/

- This is the gaussian filter, the middle of it is the pixels being anti aliased, the sides are the edges around it - what this filter does is softens the pixels arond so they gradually ramp together - it's blurring the area where they meet.

- Here's catmull rom, here it actually darkens the pixels either side of your edges so it has more contrast and appears sharper. The problem is if you've got any grain for example, the anti aliaser might see it as an edge and make it more visible.

If you're rendering at the size shown above it's going to be quite hard to not get problems with stepped edges like you have on the counter tops - they're just at a bad angle for the resolution this image is rendered at, it's just a limitation of how many pixels you have to work with. If it was print or HD you'd get slightly better results but unfortunately at this size you're stuck.