| STEP 5 [the depth] |
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Now the depth pass:
This is really a little bit tricky and there are two solutions to get the information.
If we want to use the depth information as a linear depth which means from camera to object increasing depth (for example to add Fog in post editing) we can use the following steps (this is a little bit WIP, I'm working on a better solution):
- Create a new material and rename it z_depth
- create a surface properties shader
- drop in a 'copy' object with source = 'Surface: Distance' and destination = 'Surface: Z_depth' [fig 10]
- create a default mapping in the root level of your scene with this material
- Now we store the depth information in the Z_Depth channel, but there is a problem because an image data range (greyscale) is from 0 (Black) to 1 (White) and our depth channel contains information above 1 because the distance is in absolute space. This means an object which is for example in 100 meters distance of the camera will store this 100 value into the channel which can cannot be seen in the final image, because everything above 1 will appear white. (see illustration)
- So now a little rough trick to scale this value:
- First you have to check the maximal distance between your camera and your objects, which is in this scene around 3,5 meters
- Now create a new VSL post image effect and rename it 'z_scale' [fig 11]
- Drop a Float variable inside the image processing shader and rename it max_distance, check the initialize checkbox and type '3,5' into the intial value field
- Now drop in a operation object and change type to 'max', go to the General tab and use the drop down to select the '/' operator.
- Use input0 = 'image: Z_Depth', input1 = 'max_distance' and output = 'image: Z_Depth'
- Important: don't forget to add this VSL post image effect to the default effects post image [fig 12]
- What this does is the following: It divides the value of Z_Depth by the maximum of 3,5 and Z_Depth. So we scale down the values between 0 and 3,5 to 0 and 1. Everything above 3,5 meter will appear as value 1 which means white.
The result will be this:
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To add a fake DOF in post editing we need another depth information, because we don't want the image to appear linear sharper towards the camera. We need a channel which is black around the focus and increase to white with increasing distance to the focus:
- Create a new material and rename it 'local_Z'
- create a surface properties shader
- Now drop in a curve object with input = 'surface: map coords' and output = 'surface: Local_Z'
- modify the curve as shown in the illustration and change the input sub channels to x [fig 13]
- duplicate this curve object and change operator to * and subchannel to y
- duplicate this curve object again and change subchannel to z
- Because we want the focus appear black we have to invert the value with an operation object type = 1-p1', input = surface: Local_Z and output = surface: Local_Z
- create a parallel mapping in the root level (hold down the shift button while doing this to create a cube)
- the center of parallel mapping should be the camera aimpoint
- now rotate the mapping so it's parallel to the camera direction
- after doing this you can scale the mapping so that it surrounds the scene (Just imagine there is a sphere inside the mapping with which we mask our focus). Everything outside the mapping will appear complete white in the final image.
What this does is simple: Because we use 3 curve objects (one per axis) we declare a virtual sphere inside the parallel mapping. At mapping axis value 0 our curve says the value is 0, at axis value 0,5 the curve value is 1 and at axis value 1 the curve value is 0 again. Because we multiply all values of the different axis we get white inside the mapping and black at it's border. After using the operation object 1-p1 we invert this values so the center is black and the border is white. This is a very useful technique to create local effects (like the old local scope in Real 3D V3). You can modify the curves to get even more interesting effects.
Continue to STEP 6 ...
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