Large maps rendering Faster than Small ones!

[pixeldamage]

VRay 1.5 SP2. Max 2009 x64. Dual-Quad Core, 8Gig Ram.

Hi all,

Having a weird problem. Have a high res set diff/norm/displ around 5k x 3k and the same ones resized to 1024x in photoshop. Applied to the same plane/same camera/all settings the same (I literally changed the maps over in the material editor and hit render). Result: The renders are consistent but differ in the wrong favour. The huge maps (50meg each) render up to a minute faster than the 2meg map set. I can't think of any reason!

[palibebeh]

what file format are those textures?
jpg? tiff? bmp?

[pixeldamage]

what file format are those textures?
jpg? tiff? bmp?

they are tga's and png's

[pixeldamage]

No one else had this problem?

[duke2]

A mixture or the smaller ones were pngs? Whatever the case, try to keep the formats the same from big to large and let us know how it goes! It wouldn't surprise me if png's were slower as they're compressed and VRay has to uncompress them on the fly as it renders ...I think.

[LarsSonparsson]

I think it happens because of higher sampling needed.

Smaller maps has not enough data for renderer, so it
has to do lot of calculations to interpolate values.

Example 256px map and 1000px map.
Rendering those maps out in size of 1000px

-256px map gives only every fourth real pixel to renderer and rest needs to be
calculated using some interpolation algorithm. (slow)
-1000px map is rendered out straight, because there is enough data for each pixel. (fast)

(Sorry about bad explanation, but hope you understand.)

-LarsSon

[pixeldamage]

Lars - That makes sense! Good to know, but does that mean there should be some kind of script or rule made to calculate optimum texture sizes for scenes as i'm sure many users will automatically downsize maps for optimization purposes without realising they're doing the opposite and losing out on both quality and render times!

duke- tests were all done using the same format files so for example a large diffuse tga would replace the small diffuse tga. A 2048x normal map (png) would replace a 1024x normal map (png). I don't think the problem is with the format type as I recall most of the maps were the same format and as i just described - I was consistant with replacing maps with larger/smaller maps of only the same format.

thanks to both of you for your feedback