Guest Author: Gottfried Hoffman
This written tutorial shows how to create a cool and stylized Nova-like explosion all inside Blender.
A Supernova is something mankind can’t watch too often, and there are only a few recordings of such deep-space happenings. What you can see from the Earth is mostly the remnants. The stylized nova you are about to create was inspired by the famous remnant Tycho, which is just beautiful, and a few computer simulations released by NASA over time.
Nasa Simulation Reference
3-Dimensional Flash Center simulation of the deflagration phase of a Type Ia supernovae.
Lets get started
Now that you have an animated nova-like explosion let’s add the final touches to make it even better! The first thing we need to do is add a star background, followed by a volume material for extra contrast in both color and style.
For the stars you might be tempted to use the simple stars-feature in the world settings. But that will thwart our current compositing, though, and might become deprecated in future versions of Blender. Instead, let’s create a starry background from scratch.
Add an Icosphere and scale it by a factor of two (S > 2). Now go into Edit Mode and delete the seven vertices facing the camera.
Now hit A to select all vertices, then E to extrude and S > 2 to scale the result by a factor of two again. The following figure shows what the result should look like in object mode.
Next move the sphere back 5 Blender units on the y-axis (G > Y > 5) and then scale it again by a factor of 3 so that the entire view of the camera is covered (S > 3). The result is kind of a small universe around the nova that is even usable for small camera movements.
To create the stars we will need to add a particle system. Set the start and end to 1 and the Lifetime to 250. This is the same as the start and end frame of the timeline. The emission should be set to the volume of the object and be completely random by increasing the Random value.
Before we can set the actual amount of particles or stars we need so see them clearly in the viewport. In the Render settings turn off the rendering of the emitter but keep the type at “Halo”. In the Display section set the display to “Point”.
This last step has not changed much in the viewport, but now we can change the material of the emitter. Do this by setting the material to “Halo” and adjust the size to 0.020 and the hardness to 10. The color ought to be a complete white. Now we can see the particles as small squares in the viewport while small dots indicate the vertices of the half-sphere object. Use those to select the starfield when needed. Go to frame 1 and adjust the amount as you see fit, an amount of 300 is looking pretty good. Don’t forget to turn of the velocity and gravity (in the section “Field Weights) in the particle settings or else the stars will start moving.
If we render now, we see that the current compositing is applied to the stars, too.
To get rid of that effect, we need to move the particle system to another layer. Select the object with the particle system and hit M > 2.
Now the particle system is gone. To get it back you need to Shift-Select the second layer in the layer selection box.
Rendering now will show a result that has not changed at all. To get the particle system separated from the Nova there are still a few more steps necessary. First go to the render panel and select “Layers”. Add a second layer and call it “Renderlayer.Stars”.
There you can find two different layer sets. One is called “Scene”, the other one “Layer”. Keep both layers selected in the “Scene” part. In the Layer section select the first layer (where the nova is located) for the first Renderlayer and the second layer (where the stars are located) for the Renderlayer.Stars.
Now head over to the compositor, add the new Renderlayer by hitting Shift+A > Add > Renderlayer and choose “Renderlayer.Stars” from the drop-down box.
Connect it to the viewer node by holding down Shift+Ctrl and clicking on it with the left mouse button. Then render the scene by hitting F12. Now there’s just the stars, which we can further composite on their own.
Add a glare node of type “streaks” and set the quality to “low” and the number of streaks to 6. Reduce the threshold until some subtle streaks can be noticed (0.200).
Now let’s add the nova over the starfield. Add an Alpha-Over node and connect the output of the glare node of the starfield to the upper image-slot and the output of the other glare node to the lower one. Something strange has happend:
What happend to the fog glow of the glare node? Well, the glare node does not take the alpha channel into account. In our case a good solution is to do it manually. Add a “Seperate RGBA” node (under converter) and take a look at the alpha-channel.
Now duplicate the glare node from above and add it to the alpha-output.
Add a “Set Alpha” node (under converter) and connect the output of the lower glare node to the input of the alpha channel and the output of the upper glare node to the image channel.
Now set the resulting output as an input for the lower image of the Alpha Over node and you are good to go. The procedure might seem a little a little much for a simple starfield but it will pay off once we add the volume cloud. Also being able to cope with layers pays off great, especially during animation jobs.
This tutorial will be concluded in the final part 4.