This is probably more about Photoshop than Brazil, except maybe about how best to break this up into passes....
I'm using the attached scene(just ignore the bad surface that failed to render) to test using HDRs and backplates, this being a little more 'advanced' than I've done before since the subject is in partial shadow. To get the shadows on the flying car I edited the HDR environment to get a shadow map and put it on part of a sphere, and added a directional sun light to get the shadows, and rendered out over the backplate. For the shadows on the object that looks pretty good I think, maybe a little too dark in this one, but the tricky part is getting the shadows from the car on to the ground. In the unedited shots you can see that there are sunny spots under the car that are part of the backplate, which should be totally gone, the end shadow should be the same as on the surrounding tarmac, maybe a little darker? All I could think to do was some manual Clone Stamp-ing them out, which is not exactly automatic and the end result's kind of meh. Any tips?
It sounds like what would help would be a way to get a really clean selection of the shadow of the car. There are several ways you could go about this, I suppose, but I think I just discovered what is by far the easiest:
- under Brazil's "Render Pass Control", turn it on, and then do a Global Material Replacement using a "Luma shadow mask". Presto.
I have not yet gotten into rendering in passes in Brazil, but I'm excited to see that it can provide this kind of feature!
Another helpful 'pass' would be to just render out the alpha channel of the car (i.e. the outline of the car), so that you can mask it cleanly and work on the shadow around it. The brute force way to do this would be, of course, to just hide the background stuff and render again (maybe with no lighting turned on, so it's fast) to grab the alpha channel.
I think there are two aspects to this:
1. To 'capture' shadows, use the Brazil Matte Material for that plane -- or, in fact, use 'Brazil Br_Matte Shader'. But there are a few issues, so read this discussion first!:
Your idea with transparency will not work.
2. To get shadows that match the background, see Jim's description of what he did, above - he used a 'Shadow Map' on a light from above -- this is in the light properties, and makes the light project an image. The image he used was a version of the background which he adjusted in Photoshop, so that it would have the same general pattern as the ceiling that you see in your image. But in fact that might be overkill - you could make the shadow map from some other image, or draw it and rasterize the drawing, etc. (or, in fact, model a bit of geometry!).
I hope this helps.
I didn't literally use the "projection" feature to make the "shadow map", I put an adjusted greyscale version of the hdr on a big sphere around the scene, as a transparency map, which I shone a light through to get the shadows. Doesn't look to me like that would be needed in agesandros' scene, he's just worried about the shadows of the car on the floor, for which yeah you need the matte material.
Ah, I see - thanks for the clarification! I think I invented a new feature there (the Shadow Map thing) -- I was thinking of the 'Projection' feature on a light. Anyway the way you did it is clearly the right way.
Very nice! Good model. Looks like the shadow worked well.
Hmmm... four thoughts:
- shadow from skylight overhead (as I mentioned above)
- the way the background is wrapping - I think you need to wrap on a sphere, maybe it's your environment settings? Try the GI environment if you aren't using that now... but I haven't spent much time with this, so can't give you more advice.
- in your second image, should there be a reflection of the background (e.g. the ceiling structure) in the main windshield?
- your black areas are coming out too dark, on my monitor at least - especially the roof... no feeling of the geometry from underneath. Makes me think maybe you need one more highlight, or more bounces on your Luma Server.
- front grille looks kind of wrong -- surely too transparent/thin? But I don't know how it's supposed to look.
yes...i knew these problems!!!
i must improve some elements in this model...the grid i think is thin,so appears transparent!
at the beginnig,i tryed to use my backgrond as sferical enviornment...but without success..so,after,i used a simple HDRi from internet,that i must set better!
in the second image,there aren't reflections,because,due to illuminate the car base(still too dark) i put on front of car a rectangular light(the bounces inside luma server,i think are ok,2 bounces are quite for this scene)