Rendering the same picture with different textures

[Billy]

Hi!

I have to render several pictures with the same object/lights/viewing angle but with different textures.
ie.: the packshot of a shoe with red/blue/green/glittery shoelaces on a matte grey background

Is there any possibility to compute the whole scene once and then to only compute the new color and its reflections but not the unchanged parts of the picture in order to save a considerable amount of rendering time?

Thank you for your help!

[TomG]

You can use the Render Selected option to render only the objects that have changed (along with any other objects that may be reflecting them, refracting them, or receiving GI from them - those should be selected too) and then simply overlay that on the original render in post.

[BigAl3D]

Simply put, you will have to render twice, regardless if you render the entire scene, or just the adjusted elements as Tom has suggested. I do remember, way back, about opening a 3D render in Photoshop and being able to change the 3D materials. Can't find an example of that at the moment, but I'm sure it's limited. Unless some sort of vector/pixel information from Corona can help with that.

You should get familiar with the Take system and/or Layer Tags in C4D. You can create a Take with your original shot, the dupe that and name it something else. Make sure to enable Auto Take. Activate the second Take. As you make all your material and color changes, those differences are being recorded by the Auto Take. Yes, you will still need to render twice BUT, you can now toggle between those two states with one click. You can also tell C4D to render All Takes or just the Marked Takes in one go. One click overnight, and you should have both versions when you wake up.

Hope this helps.

[burnin]

consider GI, reflections, refractions... can quickly become an issue
Motiva's Colimo and Foundry's Colorway (derivate of the former) are designed specifically with this in mind
maybe one day Corona will join ;)