Picture Viewer does not display correct colors for RenderDocument bitmap

patrick_cue

Please excuse for bumping this thread - however we tried to follow up with maxon technical support but where quickly redirected to the forums.

We are currently also running into issues, where in Cinema4D 2025.1.x the color profile for rendering seems to be "wrong" when the rendering is triggered via the python sdk.
In your projects, we use the following settings:

When rendering via CLI (Commandline.exe) or the Desktop Application this works without problem. However when using the python SDK the images come out as the "default profile" which is unfortunately un-tone mapped

The code for rendering is from AWS DEADLINE CLOUD - a render farm manager - excerpt

        bm = bitmaps.MultipassBitmap(
            int(self.render_data[c4d.RDATA_XRES]),
            int(self.render_data[c4d.RDATA_YRES]),
            c4d.COLORMODE_RGB,
        )
        rd = self.render_data.GetDataInstance()
        result = c4d.documents.RenderDocument(
            self.doc,
            rd,
            bm,
            c4d.RENDERFLAGS_EXTERNAL | c4d.RENDERFLAGS_SHOWERRORS,
            prog=progress_callback,
        )

Full function available here: https://github.com/aws-deadline/deadline-cloud-for-cinema-4d/blob/mainline/src/deadline/cinema4d_adaptor/Cinema4DClient/cinema4d_handler.py#L69-L110

It's a bit frustrating - as right now there seems to be no way of ensuring that the custom ACEScg space can be used via python.

I've also been toying around to reproduce this without Deadline cloud - and the following code showcases the problem as well:

import c4d
from c4d import bitmaps

def main() -> None:
    doc = c4d.documents.GetActiveDocument()
    render_data = doc.GetActiveRenderData()
    render_data[c4d.RDATA_FRAMESEQUENCE] = c4d.RDATA_FRAMESEQUENCE_MANUAL
    frame = 61
    fps = doc.GetFps()
    render_data[c4d.RDATA_FRAMEFROM] = c4d.BaseTime(frame, fps)
    render_data[c4d.RDATA_FRAMETO] = c4d.BaseTime(frame, fps)
    render_data[c4d.RDATA_FRAMESTEP] = 1

    bm = bitmaps.MultipassBitmap(
            int(render_data[c4d.RDATA_XRES]),
            int(render_data[c4d.RDATA_YRES]),
            c4d.COLORMODE_RGB,
    )
    bm.SetColorProfile(render_data[c4d.RDATA_IMAGECOLORPROFILE])
    rd = render_data.GetDataInstance()
    res: int = c4d.documents.RenderDocument(doc, rd, bm, c4d.RENDERFLAGS_EXTERNAL)
    print("rendering")
    if res == c4d.RENDERRESULT_OK:
        print("done")
        bm.Save("test.png", c4d.FILTER_PNG, None,)
        c4d.bitmaps.ShowBitmap(bm)

if __name__ == '__main__':
    main()

The image that is shown via ShowBitmap has the correct color profiles. The saved one is missing the display pipeline. Saving the image from the picture viewer misses the transform - only when explicitly embedding it, it is correct

Can you provide any information when this can/will be addressed ? Thank you

ferdinand

Hello @patrick_cue,

Welcome to the Maxon developers forum and its community, it is great to have you with us!

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About your First Question

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But a specific case with your specific code and data always warrants a new thread. Please also familiarize yourself with Support Procedures: Asking Questions, as while it its clear that you put effort into make yourself understood (thanks!), this is also bordering a bit on the too much information.

The bug tracked by the other topic, is that there is currently no way in the Python API to use c4d.documents.RenderDocument in an OCIO document (i.e., every document since 2025.0) and then display that bitmap with the correct colors via c4d.bitmaps.ShowBitmap. It is important to understand that:

The bitmap data generated is just fine, when you save the bitmap to disk, everything is correct. It is just that the Picture Viewer does not display it incorrectly.

The reason for that is that in Python OCIO is not fully exposed in 2025.1.0 and you cannot set the OCIO profiles of the rendered bitmap there. Internally, we have been working on an OCIO port for Python allowing for color conversions and more things, including OCIO managing bitmaps. We also added a function to bake a display and view transform into an sRGB image - another route how this RenderDocument issue can be solved.

The goal is to publish this with an upcoming version of the Python SDK, ideally the next, but as always we cannot make any guarantees. You cannot fix this issue yourself in 2025.1.0 and lower.

Cheers,
Ferdinand