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..::sun 2/2::..

Note from the author: This article was written with 3ds max 5 in mind. It should be noted that later versions of 3ds max contain an advanced particle system which can be used to create a more effective result, and a shedload easier!

The second part to this Q&A initially sees us with a finished particle setup that was generated last issue. As the majority of the leg work has now been done, all we now have to do is to set up the final materials and glows to generate the solar effect. As mentioned last issue, animations of the Sun which are produced for film and/or TV are based on UV photography of the Sun, mainly because it’s intensity would simply white-out a visible light photograph; plus if would not be aesthetically pleasing even if we managed to capture a recognisable frame as all we would see is a yellow-white blob with a few black sunspots. Therefore the majority of images in production are based on UV photography.

Images like these are widely available on the net for reference – the majority of them can be discovered at NASA’s main site after a quick search. Analysing these images helps us generate our own Solar surface texture. We could, if we wanted to, take several large versions of the Solar UV photography and generate a large cylindrical texture to wrap round the sphere, however this limits the amount of things we can do with it – animating the surface, for example, would be extremely difficult. We can therefore simulate this effect by using a procedural map tree setup to generate the large white sun spots, smaller noise encompassing these spots, and the larger rippled surface texture.

The particle systems’ settings won’t be changed so any additional effects will be handled by materials. We want these particle flares to be intense at birth and then fade off as they drift into space, therefore we can use a Particle Age map to handle the opacity of the particles. Using additive transparency generates bright spots on the surface where they are born and additional highlighted areas where particles overlap, therefore increasing their intensity around areas of concentrated particle densities.

To create the glow, we are going to use Video Post as it’s a lot easier to set up than the Render Effects and can produce excellent results in a short space of time. By using Material Effects ID’s we can link the Sun’s material to the Glow effects, of which there are two – one to generate the outer glow and an additional one to generate an edge glow to break up any harsh edges and to simulate the Sun’s Corona. Because these ID’s need to be seen by the Glow filter, rendering the particles off at the same time will generate patches around the born particles as the ID’s are occluded. We can therefore create the final image in a two-pass render – we render off the background (the sun and glows) as a single frame (or animation depending on if you use an animated material or camera setup) through Video Post, save the image out, then load this image back into max as an Environment Background image. Assign a Matte/Shadow material to the Sun Sphere object to occlude the birth of the solar flares (etc) on the opposite side of the Sun, and render off the particles on top of the background plate using the standard render dialogue (not Video Post). This works well thanks to the additive transparency, and also helps speed up render times as we do not have to calculate the Sun’s material every frame. Saying this, you MAY have some memory issues with the scene, due to the particle count, even if you didn’t have any last time. This is due to the extra memory required to calculate the particle’s materials, so if you do get memory errors then hide a particle trail system and try again.

And that’s about it. The scene can be improved somewhat with the introduction of animating the noise maps – simply amend the phase of the maps over time, but don’t go mad animating them so they move about really fast – the white spots tend to remain stationary for long periods of time, so my suggestion would be to simply amend the phase of the small noise to create a rippling surface. You may want to add extra elements to the scene such as a star field background – just don’t forget that because of the intensity of the sun, any stars will be occluded by the light, but as it’s down to aesthetics and what goes on in the artist’s mind, it’s entirely up to you!

Enlarge Screenshot Load in your completed scene from the last Q&A or load in the sun_flare01_finished.max file (supplied). Hide all particle systems and the Mesher objects and select the “Sun Renderable” sphere. In the Material Editor, select the white “2-Default” material and label it “Sun”. Check on Self-Illumination and set the Material Effects Channel to 1.
Enlarge Screenshot Add a Noise map to the Diffuse slot, label it “White Spot Shape”, set the Noise Type to Turbulence, Size to 100, High to 0.5, Low to 0.37 and Levels to 10. Add another Noise map to the Colour 2 slot and label it “White Spot White”. Set the Noise Type to Turbulence, Size to 100, High to 0.52, Low to 0.19 and Levels to 10. Amend the Output Colour Map as shown.
Enlarge Screenshot Add another Noise map to the Colour 1 slot of this map and label it “White Spot Yellow Boundary”. Set the Noise Type to Fractal, Size to 0.1, High to 0.8 and Colour 1 to RGB 255,255,0. In the White Spot Shape map’s colour 1 slot add another Noise map, label it “Orange Boundary Shape”, set the Noise Type to Turbulence, Size to 100, High to 0.815, Low to 0 and Levels to 10
Enlarge Screenshot Add a Noise map to the Colour 2 slot and label it “Orange Boundary Colour”. Set the Noise Type to Fractal, Size to 0.5, High to 0.6, Colour 1 to RGB 255,27,0 and Colour 2 to RGB 255,255,0. In the Orange Boundary Shape Noise map, add a Noise Map to the Colour 1 slot, label it “Fire Ripples”, set the Noise Type to Fractal, Size to 2, Colour 1 to RGB 255,58,0 , Colour 2 to RGB 255,135,0 , set the Output amount to 1.5 and amend the Output Colour Map as shown.
Enlarge Screenshot In the Self-Illumination slot, add a Falloff map, label it “SI Mixer” and amend the Mix Curve as shown. Add the White Spot Shape noise tree to the Front Slot and add a Falloff map to the Side slot, labelling it “Falloff Side Orange”. In this new Falloff map, amend the Front colour to RGB 255,115,0 and the Side colour to RGB 255,255,0 .
Enlarge Screenshot In Video Post, add a Perspective Scene Event. Next, add a Lens Effects Glow Image Filter Event and label it Outer Glow. In it’s Setup, un-Check Object ID, check on Effects ID and set to Perimeter Alpha. In the Preferences tab, set the Size to 42 and select Gradient. In the Gradients Tab, design the Gradients as shown to control the colour and opacity of the glow. (Continued in the Tips section...)
Enlarge Screenshot Using scene created in the last paper, materials and glow effects are added to the scene’s elements, creating an effective Sun surface and solar flares.
Download the max file! Zip file to accompany.

..::tips::..

Add another Glow event to Video Post and label it “Edge Glow”. Again, un-check Object ID and enable Effects ID. Set the Filter to Edge. In the Preferences tab, set the Size to 100 and Colour to Gradient. In the Gradient Tab, Set the Radial Colour Gradient’s flags to create a yellow (position 0) to Red (position 100), and set the Radial transparency’s Flags to RGB 45,45,45 (position 0), RGB 23,23,23 (position 1) and RGB 0,0,0 at positions 20 and 100.

With all particles hidden, render off the scene (a single frame will suffice) in Video Post. Once rendered, load it back into the scene’s Environment slot using Screen mapping. Assign a Matte/Shadow material to the Sun Renderable sphere and un-hide all of the Trails particle systems and the Small Eruptions system.

Select the 3-Default material and Label it “Trails” Check on Self-Illumination and set the Diffuse and Self-Illumination colours to RGB 255,135,0 . In the Opacity Slot’s Mask map, go to the Particle Age map and amend Colour 1 to black, colour 2 to RGB 50,50,50 and set the Colour 2 age to 5. Assign this material to the Trails particle systems. Clone this material and label it Small Eruptions.

Add a Particle Age map to this new material’s Diffuse slot and set colour 1 to RGB 255,255,0 , Colour 2 to RGB 255,144,0 at age 5 and Colour 3 to RGB 255,0,0. Instance copy this map to the Self-Illumination slot and assign this material to the Small Eruptions system. Finally, render off the animation from frame 200 onwards to enable the particles to drift out before the render commences.

Initially published: 3D World magazine, Issue 43, October 2003.

Copyright Pete Draper, October 2003. Reproduction without permission prohibited.

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