Hi All,

I have my scene setup and it looks great in the preview, however when I render to file the scene is all dark?

Does anyone know why this would happen?

In the image you can see my screen render and the preview from the file render.

I only have one mantra node in my output network.

Your render is by default in linear space. In your mantra rop turn on gamma 2.2 .

rob

I did check that and my only output node was set to Gamma 2.2 for Color Space under the Shading TAB.

However, I was rendering to PNG files. When I switched to TIFF the lighting worked again. I guess there is some kind of bug in the PNG output. It seems to be related to using 8 bit integer as well. In other 3D programs I can render to an 8 bit JPG or PNG and the color is preserved. In Houdini this does not seem to be the case.

I am rendering a 1280x720 and getting files in the range 5MB per frame for TIFF while JPG is only 29K. A file size somewhere in between would be nice.

no bug
Color space in Shading tab is just for sampling, it doesn't change color space of resulting pixel values, they are still linear

if you save linear image as float tiff or exr or other formats that are considered linear, everything should be ok, since many programs read them with applied correction on top automatically
if you however save format that is considered sRGB as jpg or png or most 8bit formats, the image values saved to file are still linear, but the programs reading that file assume that gamma correction is baked in and will not apply any on top, therefore it looks darker

to bake gamma to your image you have to add vm_gamma property to Mantra and set that to 2.2, that will bake gamma to file (which will cause opposite problem if you save exr etc.)

Thanks Tom, that was it.

For new users, I'll just explain how to do what Tom mentions…

Select the Mantra node and in the properties activate Edit Parameter Interface, under the gear icon, for that node. You will see two columns with a bunch of properties in each column. In the left filter field near the bottom type ‘vm_gamma’. This is the non-exposed property that Tom mentions. I found it under Render/Output folder. Once I located it I dragged the property from the column on the left into the column on the right. You can move it up and down the stack to make it appear where you want in the property sheet. Once you drop it click Accept.

Now locate that property in the property sheet (which is generically named Gamma) and change it from 1.0 (linear) to 2.2 (non-linear). You also will have to set the Quantization to 8 bit Integer. Then pick a valid container type for your image, such as JPG or PNG.

That did for me. Now I can render to 8 bit PNG files.

Quite frankly I think the drop down, Infer From filename, should handle this behind the scenes. But it is nice that you can at least manually configure this.

I guess real professionals don't use 8-bit eh?

Enivob
I guess real professionals don't use 8-bit eh?

It would be anti-professional to use it Once you spend the time to render it you want to keep as much data as possible to allow compositing or further image manipulations. You can use Houdini built-in compositor, aka COPs for Compositing Opertations. Check it out, it's pretty powerful. At the very end of all your work, people will view your work at 8bits if it's on Vimeo, YouTube or web Jpegs etc

In almost all cases you render to a floating point format in 32bit, i.e. EXR, for data passes, and, perhaps 16bit for RGB. 8bit integer just doesn't have the quality needed for further processing.

Enivob
.

Quite frankly I think the drop down, Infer From filename, should handle this behind the scenes. But it is nice that you can at least manually configure this.

MPlay has this option. If you set your Mantra ‘Output Picture to ’ip', for Image Player, then it will render to MPlay, where you can save image or sequence with ‘Convert to Image Format’s Colorspace.

You can also always request feature enhancement, RFE, in the Support menu above.