CISC/CMPE 454 Assignment 1B (Lauren)
You task is to implement non-photorealistic rendering on the GPU.You
will add cel shading and a wide black silhouette to a rendered model.
Rendering is done in three passes:
– In pass 1, the object is rendered and the colour, normal, and depth
is stored for each pixel.
– In pass 2, edges are detected by computing the Laplacian of the
depth at each pixel.
– In pass 3, the object is rendered using cel shading (i.e. quantized
diffuse shading) where the Laplacian is below a threshold, and
using a black outline otherwise.But this would result in a black
outline that is too narrow so, instead, a fragment is coloured
black if any of the nine fragments in the 3×3 neighbourhood around
the fragment has a Laplacian at or above the threshold.
The colour, normal, depth, and Laplacian are stored in four textures.
Each texture can be thought of as having the same dimensions as the
window, so there’s a one-to-one correspondence between texels in the
texture map and pixels in the window.
You do not need to edit or compile any C++ code.You need only to
edit six shader files: a vertex shader and a fragment shader for each
of the three passes.
But you should look at the C++ code to see how things are done.In
particular, Renderer::render() is the key function to perform the
three passes, while GBuffer::GBuffer() sets up the four textures on
the GPU.
Step 0
Compile and run the code.On Linux and MacOS, use
make
./toon data/teapot.obj
On Windows Visual Studio, add data/teapot.obj to the command-line
parameters in the debugging configuration.
Explanation of output:
The program should show an empty magenta-coloured window.Press
‘d’ (for “debug”) to see the output of the “dummy” shaders, which
just render the object.Then press ‘d’ again to see the four
textures as they appear after the first pass.Press ‘d’ again to
see the textures as they appear after the second pass.Press ‘d’
again to see the program output (i.e. after the third pass).The
textures will be shown as
lower-left= colour
upper-left= normals with (r,g,b) = (x,y,z)
upper-right = depth with lighter being larger (i.e. farther away)
lower-right = Laplacian with lighter being larger
After the first pass, the Laplacian texture isn’t updated, so it will
appear stationary as the other three get updated.Whatever was last
in the texture will still appear there.
Using the provided skeleton shaders, the textures for colour,
normals, depth, and laplacian will be red, green, grey, and blue,
respectively.The object will rotate in the first three textures,
but the Laplacian texture will initally be completely blue.You
will have to edit the shaders to provide correct textures.
Step 1 (Pass 1)
[2 marks] Edit shaders/pass1.vert to correctly compute the colour,
normal, and depth.These are passed to the fragment shader, which
will store these values in the corresponding textures.You do not
have to edit the fragment shader in shaders/pass1.frag.
When you run the program, press ‘d’ twice to see the three textures.
Step 2 (Pass 2)
In Pass 2, *all* pixels on the screen are written to, so a fragment
shader will be executed to each pixel, even if it is a background
pixel.
[1 mark] Edit shaders/pass2.vert to compute texture coordinates from
vertex coordinates.
[3 marks] Edit shaders/pass2.frag to compute the Laplacian at the
fragment.This will involve sampling nine values from the depth
texture in the 3×3 set of texels centred at the fragment’s texture
coordinates.
When you run the program, press ‘d’ thrice to see the Laplacian
texture in the lower-right corner.Bright pixels will indicate
large positive values.
Step 3 (Pass 3)
In Pass 3, again, all pixels are written to, so a fragment shader is
executed for each pixel.
Copy shaders/pass2.vert to shaders/pass3.vert.These two vertex
shaders should be identical.
[6 marks] Edit shaders/pass3.frag to compute cel shading and
silhouettes as described in the comments in that file: Have a
silhouette that is black at the edge BUT A BLEND of black and the
Phong-computed colour toward the object interior.Make sure that
the shader is efficient and does not make unnecessary texture
lookups in doing this.
To Hand In
[-1 mark] One mark will be deducted if these instructions are not
followed exactly.That’s because, in this case, the TAs have to
spend more time dealing with the exceptional (not in a good way)
submission.
Make a directory called ‘a2’.In that directory, put
– your SIX shader files
– a README file with your name(s), student number(s), and email address(es)
– one screen captured image of your program output
Create a ZIP archive of the a2 directory.
Submit the archive to OnQ.
ONE MARK WILL BE DEDUCTED IF THESE INSTRUCTIONS ARE NOT FOLLOWED EXACTLY.
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