Extracting a ground plane from one of the HDRI included in the Summer Light HDRI Pack.
Sometimes you just want a quick and simple way of making a ground plane that matches your HDR so that you can render some movement in your scenes. This is a fairly straightforward little trick I use to do that. First I start by taking the high resolution HDRI (ours are usually 16000 x 800) and converting it to an 8bit image in Photoshop.
Then I load it into PTGui and make sure I have the image set to Rectilinear, rotate it by -90 on the pitch so we’re viewing the flattened out ground. Then I use the sliders to chenge the field of view to around 175 x 175, just enough to get most of the ground up to the horizon. Note, becasue you’re essentially warping an already warped spherical image taken from one viewpoint the edges are always going to be blurry and warped looking. Thats becasue we’re flattening out the pixels in the far corner of the original fisheye images where there is very little detail.
Once thats done we render the panorama out of PTGui at 15000 x 15000 pixels (or whatever size you like, I like to have a large detailed map) and bring it into Photoshop and use the clone tool to paint out the sun reflection.
It’s then just a case of extracting the maps we need. I used diffuse colour, reflection, and normal for this quick test but you can extract bump and gloss if you like too. I also refined the normal map by adding a flat colour over the most reflective parts to make the reflections there flat.
In modo we make a circular plain and apply the diffuse colour, reflection amount and normal to it. The HDRI is also in the scene as the spherical environment.
We also need to fade out the edges of the plain with a transparency map
This is the result, Note that I have yet to add the flattened puddle version of the normal map here.
Watch the final animation
You can download the maps I made using this technique below:
Get the Summer Light HDRI Pack hereGo to Summer Light HDRI Pack
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