Searching a true model of curtain.

[bertrand125]

Hi,

I'm searching a true 3D model of a curtain, that is made of strings and not of a transparent surface. If a such model exists, I hope it will render better because it is not a transparent but a pierced material.

Actually, I'm using a transparent curtain and I'm trying to illuminate a room through it. So I placed an unviewable light panel between a window and the curtain. I set the light power to 30%. I also modified the MTL file of the curtain to set the opacity to 0.15 instead of 0.66, in order to make it more transparent.

With these settings, the illumination of the room seems more natural, but when we look at the window, the curtain appears too much transparent.

I know it is possible to set a different opacity for each side of a surface. But if I find a curtain model that uses different materials for the two sides of the curtain, I think it won't render correctly, because the surface is made of waves and the light go through the curtain several times.

[hansmex]

Search the Sketchup Warehouse for strip curtain or string curtain. Both may give useful models. You may have to install Sketcup to delete unwanted parts of the models.

H

[bertrand125]

Thanks for reply, but I'm searching more traditional curtains, that look like the curtain on the free 3D models page.

And I don't think I will find it, because I computed the file of a such model should be very big, because of the high number of strings, each string being divided into a lot of little parts in order to make the waves and a natural shape.

So I decided to make a little program in C language, that create a .obj file to store a very basic curtain, usable to do some tests, because I'm not a good 3D graphist.

For a realistic number of strings, and a size of 60 cm on 140 cm, the .obj file generated takes around 400 MB unzipped and 41 MB zipped, but smaller models of around 100 MB can be generated for tests.

When I illuminate a room placing a light panel behind these curtains, the lighting of the room and the shadows are very ugly. The following picture compares the lighting with the two curtain models:



So it seems the renderer have difficulties to compute a good lighting and the shadows when the light go trough a lot of little holes.

In the tests I have done, if the string curtains take big files and a lot of memory, they however was rendered faster than those made of transparent surfaces.

[alaX]

Have you tried opaque material (d 1) with transparent texture? For example white grid on transparent background (holes):
grid-white-transparent



I didn't have time to render better quality (gi "path") image and that's why I added light panels to illuminate the curtain frome the inside (and one light panel is outside the window). Texture size 0.5x0.5cm.

For tiny patterns you should probably increase AA values and/or change filter ("bucket" sampler algorithm) or increase image size ("ipr").

[hansmex]

Looking at your pictures, it seems you mean "vertical blinds".
I made a few tests.

1 - I went to this website that has loads of transparent textures.
2 - In the Sketchup Warehouse I found a nice set of modular vertical blinds .
3 - I then made a few renders, applying a transparent texture to the blinds.

right image - Q4 using PVR with default settings, in the renderer I checked Enhance External Brightness, unchecked Add Ceiling Lights, 800x690 pix, rendering time 6-7 minutes
left image - (probably?) same settings, but I added a halogen light in the exact middle of the room (strength 50%, 100x100 cms), 800x690 pix, rendering time 49 minutes



original image

[bertrand125]

it seems you mean "vertical blinds".

No, on the right photo, I don't remember precisely the test I have done, but I think the curtain had too big strings, so it isn't enough transparent, and it may seem to be blinds because of the waves.


@alaX: I have created a Q4 PVR photo using your tip, opaque material and transparent texture, and it also causes a problem on the illumination of the room. But the good point is that the curtain is less transparent than the model I have, made with a "d" value set to 0.15 and an opaque texture.

The model is also much smaller in .obj file and I think also in memory, than my curtain model made of strings. I managed to reduce the size of my curtains to .obj files of around 200 MB unzipped, letting the software compute the normals automatically, but it is probably the same in memory.

For tiny patterns you should probably increase AA values and/or change filter ("bucket" sampler algorithm) or increase image size ("ipr").

I will try to change these settings. I didn't do a lot of tests because of the long rendering time in Q4.

[alaX]

plain white texture with transparency - white50%.png



Better get used to "cheating" - it won't be anything wrong if you add lightources to make room more illuminated.

[Bubblobill]

Curtain.zip

[Mike53]

Thank you for sharing the curtain Bill, works a treat. link
Mike

[Bubblobill]

Wow, that does look good. Far better than I expected.