Adding a Background Post-Render

What do you guys think of this? Somewhat believable? I’ve stared at too many variations I think my brain is having a hard time telling if it looks right haha.


Now you’re getting there! That looks pretty good. I think you should stop now. :smiley:


Yes! As one of my teachers always said “better is the sworn enemy of good enough”.


Alright! I still have a few more views of other parts of the project to do, but I think I have the general idea now.

If anyone is reading this thread in the future and wants to know how I got the shadows to cast on the image in PS here’s what I did:

  1. In PS, sample an average color of the background grass you’re using.
  2. In SU, add a large rectangle on the ground plane of your model, color it with the same color you sampled for the grass.
  3. Render the model and a mask (be sure to turn off the grass rectangle when rendering the mask), and import into PS and apply the mask.
  4. In PS, use the magic wand to select the shadows on the grass color in your render.
  5. Switch to the mask, and use a brush with about 10% opacity to repeatedly color in the selected shadow areas of the mask until you like the results. You’re basically adding some transparency to the mask so that the underlying shadow on the model shows through. As long as you don’t go too far with it, the texture of the background image will still show through strongly enough to make it look realistic.
  6. I also softened the ages of the mask where it meets the model so they weren’t quite so harsh. I’m sure you could get really creative with a custom brush shape to simulate blades of grass popping up in front of the model if you wanted to.

Thank you all so much for your help! I would not have succeeded without you. Hopefully the more times I do this the better I will get. I think the biggest factor in getting it to look right is getting the perspective, focal length, etc in your model to match the photo you’re using.


That’s a great line. I haven’t heard that one before.

That looks real enough for me! Let’s get some steaks on it.

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I think you’ve done a fantastic job! I hesitate to even add an observation this late in the game, but I think one more simple adjustment may help. In the image below, the red lines indicate the vertical orientation of the perspective view from SketchUp while the green lines indicate the background verticals.

This makes things look askew (at least to my eyes). If you can stretch the background image along the top to skew the image, it might help it look more natural.

Here’s a photograph that’s similar … note the verticals in the foreground and the background:


may i know in which render software ur rendering:thinking:

Great observation! It still did look a little off to me, but I couldn’t put my finger on it. I think you nailed it though.

You can find it here.

Hi all,

It’s a steep and endless learning curve for all this! I use Twilight free edition too.

For me the bricks of the structure perhaps look a little flat. I tried to find the same brick texture as you but this was the closest I could get. Did you add a bump map to the textures to try to give the illusion of a bit of depth? (I know my paving scale is set too small but oh well…)

Somewhat a revelation for me a few months ago was exporting a 2d file of the shadows only, as a nice fast way to get correct shadows onto a background image. I would do the same as you to get the correct ambient occlusion type shadows on the model - ie. the green reflections in the shadows on the right pillar on the model - I couldn’t download your model, so I quickly made another and super-imposed it over a copy of your image, just to get the grass background… So, in Photoshop I paste in place (ctrl+shift+v) a shadows only image (same pixel dimensions as the render) and put it in Multiply mode to get rid of the white. Then you just play about/can stick it in whichever layer position you feel best to give the best look. Hope that makes sense - just though I’d share :slight_smile:

I know it’s all done now, but I think you would have been been better if you had started by using the background as a matched photo (File | import | jpg - hit the option button for “as matched photo”)

This would allow you to mark the horizon and 2 point perspective. The image you export could be combined with the background in PS to soften shadows.

I did not add a bump map. I don’t know how to do that, i’ll have to look into it.

I like your shadow layer idea. How do you render a “shadow only image”?

Another great idea. I did a tutorial on photo matching a long time ago, but I’m not super confident with it. I’ll have to play around with this.

The shadow idea is a powerful technique, searchable tutorials on the interweb, such as this one:

…used a lot I believe to export ‘ingredients’ from Sketchup (or 3DS Max or whatever) into image editors so you can be flexible and get creative in the image editor. Everything saved onto a different layer means you have lots of flexibilty and control over the finished looks. So for the shadows only:

  1. Change the Style to Hidden Line with White Background, under the Edit tab remove/uncheck Edges - so all you have left is an image of the shadows and everything else just white. If there is anything else showing, just uncheck everything, except shadows… Don’t forget axes and constructions lines :slight_smile:

  2. You can then save the 2D image (File>Export>2D Image) with the same pixel dimensions as your Twilight Render (in the ‘Options’ sub-menu next to the Export (Save) button at the bottom).

  3. Load everything into Photoshop (or Gimp, or Serif DrawPlus etc.) and paste-in-place each ‘render’ all into one document on different layers.

  4. Play about and make it look cool :slight_smile:

Ahhh how about that. I had no idea the export 2D image option even existed. I’ll have to play around with this. Thanks!

Just a hint - more shadow on the right to be a closer match to inside the unit and the grass shadow above the unit.

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An old thread, I know. But another method of convincingly merging a model and a background image is to take the jpg and raise its mode in Photoshop from 8 bit to 32 bit before saving it as an HDR image. Then you can specify it as a both a background and an environment and take the lighting directly from the photo. If you can take panoramic shot, so much the better.
If the rendering package has a shadow catcher facility, then you don’t have to fake those either.

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Following @AlanF cue on resurrecting an old thread to add new tips, this issue of matching a SU model to a photo has long history in the SU forum. Joshua Cohen uses the Watermark tool along with Advanced Camera Tools extension and Match Photo to make his presentations. Joshua’s technique.

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This work is not bad. But i think here are coloring problem. Moreover the house is not focusing in this tutorial. Otherwise all are fine.