Frontal Projection

The basics

Texture Files
Frontal projection is a great way to add 3D models to a detailed back drop image and extremely fast to render
Create a plane in Sketchup, this will be the model that we will use to project the image on.
The size of the plane depends on the background image that is being use, it comes down to blending the background with the plane, the bigger it is the easier it is to blend.
Place the detailed model on the plane.

Add the image

Create a new material and give it a useful name like 'frontalmap' and add the background texture called 'scene.png',
Scale doesn't matter as setting the uv property in Thea is all it takes.
Apply the material to the plane

Setting the Thea properties

Open the Thea 'Tools Panel' and set the material property to editor (1)
Set the projection to 'Front'
Do a IR render and the plane should look similar to this

Adding the ibl image

Select the 'Enviroment' tab in the tools panel and click on the 'IBL' icon and add the 'light.exr' image to the first property 'Illumination'', and check the checkbox.
Run IR and use the rotation property to make the IBL map match the image on the plane
Make sure the sun is turned off

Add the background

Staying in the Enviroment tab add the background image 'scene.png' into the 'Background' settings
Set the 'Wrapping' to 'Fit'
With IR running, adjust the 'Intensity' so the background brightness matches the floor plane
That's all there is to it... but what if we need more.....
Complete scene

Reflections with Frontal Projection

The 3D object is on a tiled floor which has reflections in the arches, but the 3D doesn't have any reflection.
With a simple mask and two layer material reflections can be added.

Creating a mask

Mask Files
A mask is a simple black and white image, the white area outlines the tiled area of the floor.
scene was created in 3D so I used a normal channel pass edited in Gimp to create the mask.
to make the transistion between black and white less obvious I feathered and expanded the black into the white.

Adding the mask

Select the material icon in the 'tool panel' and add the mask norm2.jpg into the basic mask slot.
Change the projection to 'Front'
If you do a test IR render you will notice the wrong part is maskde on the floor plane, I had a brain fart and and and did the mask wrong, simply invert the texture in the 'Tone Mapping' properties.
Run IR and the floor should render black, feathered at the edges

Reflection layer

Select the basic layer, right click and duplicate, select the duplicate layer and remove the mask
Drag the diffuse image into the reflectance slot.
Run IR and adjust the roughness amount until you are happy with the reflective amount..
do a production render and the jobs a good un!

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