optimising distance tex rendertime. help?

[super gnu]

im trying to cut a model using a distance tex.

its a very complex model, and a very complex cutter.

ive tried with the vrayclipper, but its *incredibly* slow.

ive tried simply using the distance tex as a mask between the base materials and one 100% transparent with opacity set to clip (i dont need the capping that clipper does) . this is faster, but still like 5hrs a frame for 1080p.

is there -anything- i can do to speed things up?


i could cut the model into smaller chunks, and make a seperate cutter for each object, and a seperate distance tex for each chunk, but this is a load of work, so i dont wanna do it if it wont help speed things up..

would it have a major impact on speed if each distance texture had less faces to check against? consider the overall amount of clipping done would be the same.

anything else i might not have thought of?

note: its animated, so i can forget old fashioned booleans.. they would freak out.

[vlado]

Which V-Ray version are you using?

Best regards,
Vlado

[super gnu]

a very recent nightly (after you fixed the proxy saving issue)

edit: its 26580

[super gnu]

i also even tried vraydisplacemnt on a very small value with water level set to cut, but that looked awful and ate loads of ram.

[Morbid Angel]

I had such issue before. I had to cut holes in a complex mesh using distance tex, as soon as I did, though the holes were small (asteroid debris through ships hull) the entire model rendered 3-4 times slower so render time went from 60 min per frame to 4 hours.

Solution was to use vray dirt, and have an include list so that object which cuts the whole is only the one that produces occlusion with a short radius it gave me the clipping I needed and was fast to render.

[super gnu]

hm, i tried that already , but when i did i only got a thin cut at the face boundary, the dirt texture doesnt shade inside of the cutting object, just at the faces so doesnt cut a complete hole.

id love to know how you got it to work..

[super gnu]

btw, apart from the speed issue, distance tex is currently my favourite map.. so useful.. i cant imagine how i coped without it.

[Morbid Angel]

I didn't do this in max, but here is the tutorial I referenced. Though it uses distance texture, its essentially using distance texture as an opacity mask so vray dirt works too.

http://therenderblog.com/render-time...aydistancetex/

the problem i can imagine is that on large scale geometry there might be some oddness, I had small holes so it was fine.

[super gnu]

yeah its basically the method im using, but my issue is if you for example, intersect a sphere with a plane, and use a distance tex on the plane, you will have a solid circle where the sphere is, with a fallof outside.


with dirtmap (maybe it works different in maya?) you will have the fallof outside, but inside the sphere boundary it is not solid.

this means as a cutter, the sphere will cut a ring out of your plane, not a circle.

this was my result when testing anyway..

maybe if your cutter was tiny,and dirtmap was set to 2sided, and the radius of the dirtmap was bigger than the internal space in the cutter, it might work?


im slicing up buildings using building sized cutters.. not sure it could be made to work.

i will give it another look though, maybe i missed something.

[Morbid Angel]

yeah I see what you mean. In my case that didn't make a difference my objects were small as I thought. Can you use a volume object like a cube instead of plane?

[super gnu]

i tried again with my model, and it seems as i feared, i dont get proper cuts, holes just close to the faces of the cutter object, not "solid cuts"

and surprisingly, with "consider for gi" enabled (necessary if i want light inside the cuts) it rendered slower than the distance tex, with the lightcache particularly, taking an age..


in the end, i dont think its actually the distance tex that is the whole problem as such, its reasonably speedy as a diffuse map for example.


the issue is probably split between that and the cutting method,.. im not sure how vrayclipper works, but both that and masking to a clipped transparent material are not very fast. at least we now have the clip option for the opacity map. with normal opacity it would have been much worse!

- tried with a simple b/w noise map to cut, and it was faster than distance tex, but still not exactly speedy, 2 hrs a frame instead of 5..

[super gnu]

i wonder... i can see when i render that the areas that are 100% using the transparent material are still really slow to render. (f.e. at the start when the whole model is "invisible" it still takes 2-3 hrs a frame to render.. )

is a 100% transparent material (black vraycolor in opacity slot) set to clip, the most "nothing" material possible? could a theoretical "null" material be made that would literally just be ignored by the renderer in every sense?


or is the slowdown i see in those areas going to be caused by the renderer shooting rays just to do the distance tex calc and actually decide what material to use?

gah i had assumed that at least it would go faster at the beginning as there are no actual distance tex intersections yet, the cutter is under the floor, and the building is completely invisible.

probably the slowest rendering grey untextured plane in history. maybe ill upload it to the image section when it finally finishes.

[svetlozar.draganov]

Have you tried to bake the distance texture and use it as a regular bitmap instead?

[super gnu]

no because the geometry is incredibly complex, and i need a plug-and-play solution.. ive ditched the option as it was just too slow!

[Deflaminis]

I highly recommend Rayfire slice. Even caps the hole. Never used it on a 50M poly object but works well for me. https://www.youtube.com/watch?v=JC31kXxYzl4