Cineversity

I’ve rendered a video out to an image sequence of .pngs with alpha. I created a standard material and applied the image sequence, calculated to load the stills, and checked “animate preview”. I applied the alpha to the alpha channel similarly.  I applied this material to a plane and everything works and looks right in the perspective window. I created a light and enabled shadows to be cast onto the face of a background cube. 
But the shadow being cast is of the plane carrying the video, not the outline of the alpha channel. So now my video is casting a rectangle as a shadow. 
I’ve tried applying compositing tags to each with no luck. This seems simple but what is my simple mind missing? 

My skill level with C4D is novice.

Brian
R21
iMac i7

Hi Brian,

Please check your Private Message here on Cineversity, I have sent you an upload link.

You might test this file here:
https://www.amazon.com/clouddrive/share/H3QCehfFfsmJBbMcoAVz3MAvttoGdyIJgXjo6W9ZBCd

Personally, I never have used in over three decades any PNG in production. It has no real alpha, just transparency to my knowledge; Which is kind of limiting.

I will have a look at your file ASAP.

All the best

Thanks so much for the quick reply. I tried the test file and it appears to be exactly like my set up, but I don’t see any shadows on the plane in your file. I did check all the settings on the lights and in my project when I switch to hard ray-traced shadows IT WORKS.  If I toggle back to soft shadows I see the rectangular shadow cast by the plane, toggle to hard and the alpha is represented by the shadow.
Based on what you said about PNG, I’m re-rendering tonight in PSD.
Very helpful, Brian

Hi Brian,

That is weird, as I have set up the three lights with three different shadow types, and all work here. Whereby I do not recommend to use Soft Shadows in animation based production, though. Lights have over a hundred parameters, which are set up in the scene file, it is impossible to communicate those adequately in any other form.

Here is a screenshot of what I see here.
https://www.amazon.com/clouddrive/share/YL4d2SMMaTxV0Vq4i2FNzU5tliqQrLwLNXN5IXv9Yvt

I typically request the scene file, and in your case with one of the sequence files. This is usually the fastest way to clear things. I’m not happy to make a long list of wild guesses and have the artist on the other side testing all of them. It is routinely a waste of time.

I have sent you an upload link, you can upload both (project file and one PNG) to it, if the file carries the word private in it, I will recreate it so I can share the results. I believe in forums work, one question, and shared to the benefit of many. I would use as often as possible OpenEXR files, btw.
So, if I get some material, I’m happy to look into it.

My best wishes

Thanks for the file, Brian.

Set the Texture Tag> Tag> Side: to Both instead of Front.

That should be all. (Files are the key, so thanks again!)

The Soft Shadow was set to Shadow> Shadow Map 250x250. This is relatively low. I’m not aware of your background, so if you know this light-mode, ignore the following. However, since I write in a forum, I have to answer a little bit broader.

The Soft Shadow is a relic from an ancient time. It doesn’t really calculate any shadow.

In fact, it is just a fake.
It measures the space that it covers with its light. This space is probed. This is not done continuously! Points are set in space, and the information of these points reads more like this: Object a is behind me, object b not. This creates the shadow map, pure information, not anything remotely like a texture.
With many of those points, the final interpolation is done. If one of those points is behind an object, the next object will be darker. If one of those points comes closer and moves through the polygon, but the neighbor point not, some imprecision will happen. Hence why I hope this type of shadow is NOT used for animation. It can flicker, or pulse, or…

Yes, it is fast, I know, and that is the reason why people love it. But in the end, after the rendering is done, quality is all that counts.

All the best

Thanks for looking at the file. I thought I tried everything including that. Makes some sense. The light was blocked by the plane when the texture was only on the front.
So based on what you say about soft shadows, if I wanted to soften the ray-traced shadows is the best way to output a multipass shadow and deal with it in the compositing?

I’ve also tasked myself with re-making the textures with the node-based editor (which I’m trying to learn) Onward, and thanks again.

Brian Williams

Hi Brian Williams,

Nice that it works now. It is kind of counterintuitive that it works with any but the soft light (with front).

The best shadow quality, considering the hard to softness, is based on the Area shadow. The raytracing shadow is always hard. Except you move it quickly and have, for example, “Sub-Frame Motion Blur” on. That was an accidental effect two decades ago in a different application. However< I don’t really think that it has an advantage over the area shadow/light.

Blur it in “post” would perhaps be possible, but required that you have the shadow without the shadow casting element; otherwise, you might get a seam around the foreground object. So two render sessions would be needed. Which might help for post Depth of field effects or even motion blur. (Which is by itself a set of problems, when mixing practical footage with motion blur and CG based motion blur, it can add naturally to it, but a camera move that counters the content of the practical footage can look weird. (Think of an actor moving his/her hand fast and have it blurred based on that. The 3D camera moves with the hand and blurs everything else, but one would expect the hand, subjectively not moving, to be free of motion blur. I mention that only as practical footage and 3D render must agree to each other, even we look only at the shadows.

I mention the Soft-Shadow problem from time to time, as the main difficulties show mostly up close to a deadline. I think it is better to make aware when time is not that critical.

My best wishes for the Node Material exploration. It is like Fusion or Nuke (etc.), and it will allow for many new work-flows, compared to the standard materials.

Stay safe, stay healthy.