[ bryce deep impact ]

This article focuses on how to render a scene that simulates the impact of a celestial body (meteors, comet etc.) on land. It was inspired by the movie Deep Impact. I was amazed at Deep Impact's visual effects and wanted to recreate them in Bryce.

Note: The procedures and techniques mentioned here are guided suggestions. The article is written to show how I setup and rendered the scene. You are encouraged to modify any of the steps to further your own artistic exploration.

scene setup
The image ratio (document aspect ratio) is 2 : 1, which is a horizontal format. Because I am dealing with a wide landscape scene where huge explosion and shockwave occur, the horizontal format will enhance the visual impact of the image.

I banked the camera to the right a little to give the image a personality.

Composition
Using the good old Rule of Thirds, the impact will be situated between 1/3 to 2/3s of the image.

terrain setup
There is no definitive rules on how to design and arrange a landscape scene. You need to build a landscape that most pleases your artistic vision.

Here are a few suggestions that will help you build similar terrain setup to my scene.

1. Terrain height is dependent on your impact size; the larger the scale of the impact, the lower those terrains should be. This guideline enhances the miniature sense of the landscape. Play around the terrain resolution to achieve believable detail on the terrains.
2. The impact site should be flat or indented below surface level. This guideline reinforces the visual cue that 'destructive wiped out anything on the spot.

This image shows one of my terrains in Terrain Editor. The terrains I used are rather simple. I used the default 125 resolution and eroded the terrains.

This image shows the layout the terrains in the scene. Here, I use 3 terrains for close up and 3 in the background. The impact spot is void of any objects. Try not to put too many terrains into the scene or it will lack the destructive feeling we are aiming to create.

Tip: Always try to use more than 3 terrains in a large scenes. This not only increases the detail of your scene, but allows more flexibility in the design of the scene's layout.

terrain material
I used "Eroding Cliffs" from 'Bryce Rocks & Stones' default materials. Materials are dependent on your own preferences and scene setup. Most of the Bryce default 'Planes and Terrains' materials are usable, such as the "Classic Bryce Snow". However be careful as snow sometimes does not enhance such scene but will spoil it.

Of course you are free to make your own materials; combinations of DTE results and presets sometimes yield cool looking textures for a mountainous terrain.

sky setup
My impact scene is set at night. The reason I choose to render a night scene is that the dark sky both enhances and contrasts the impact's explosion.

Here is the settings of the scene sky.

• Sky Mode : Atmosphere off, black color.
• Haze : 1, roughly 90% black.
• Cloud Height : 3, Sky Dome color in black.
• Sun : white yellow color, 45 degree from horizon and slightly to the left opposite camera position.

The rest untouched.

Haze is minimally used here to avoid artifacts in the impact explosion. Set it around 1 with a dark grey color to enhance the depth cue for the background (distant) terrains.

The sun rather than the moon acts as an overall light source (not the main one however). The white yellow color is to reinforce the later explosion color scheme. You will probably be wondering why we are doing this; the sun will render the terrain as if daylight. The sky dome, however, will save the day!

The sky dome acts like a filter to the sun. Setting it to a black color reduces the diffuse sun color on the overall scene. A picture is worth a thousand words. The two images below illustrate the differences in scenes created with the sky dome color in white (equal to off filter state) and black.

(Note): Of course you can control the ambience and diffusion level directly in the terrain materials which is an alternative. But controlling sun and sky dome give you more consistent, overall and instant control over the scene.

trail and bubble
First, construct the trail of the celestial body (comet or meteor) by using 2 cylinder primitives. The outer cylinder with the larger diameter surrounds the smaller cylinder. The outer cylinder is used for a feathering effect while the inner cylinder forms the core celestial body trail.

Then create the bubble, which is the explosion sphere. Create an ellipsoid, scale and place in under the trail such as in the image below.

Apparently in Bryce 2 for Windows, there is bug where 2 intersected objects in 'fuzzy' shading mode will produce artifact rendering. See the above image. There will be a hollow rendering at the intersection space. Other Brycers have suggested that setting both in positive attributes will cure the problem but it never works in my machine.

Therefore I use a work around method by placing the bubble in front of the trail and avoid intersection. Figure 4c and 4d show the top and camera view for the bubble placement.

If you are using Bryce3D or Bryce 2 for Mac, you should have no problem in this. Therefore you can safely intersect them.

[Ed.note-Unfortunantly this problem also can occur to a lesser extent in Bryce 2.1 for Macs. Retouching the intersection line in Photoshop is often easier than rearranging a large and complex scene.]

trail and bubble materials and lighting
This portion is largely a field for exploration. There many combinations of materials and lighting that will give incredible visual effects. Here is what I have discovered works best for this type of scene.

materials
To save writing space, the material settings will be displayed in images as seen in Material Editor. In both images you can click to take a closer look at the settings.

For the outer trail, the setting in the Material Editor to the left. [figure 5a]
For the inner trail, the setting in the Material Editor to the right. [figure 5b]

Both are in 'fuzzy' shading mode and channel A scale in 99. The world top mapping is used to create the trail lines on the cylinders.

For the bubble, the setting in the Material Editor below.

However, the shading mode for bubble is 'fuzzy additive'.

lighting
The scene uses 2 radial light sources. One is to lit and creates a bulge on the trail while the other one is to lighten the bubble. See the image below for their placement.

In a static image, it is difficult to convey sense of motion. Motion blur is a popular solution for both animation and static rendering. Since Bryce 2 and Bryce3D don't come with the motion blur feature, the light bulge provides for a sense of motion in the scene, by creating the effect that a second celestial body is following the trail for another impact.

The trail radial light source uses default white color with intensity of 92 and 0 falloff value.

The bubble is the heart of the explosion. A second radial light source is place in front and above the bubble to light it up. The combination of transparency material, fuzzy addictive shading and the close light source, make the bubble explode with brightness.

The bubble radial lightsource uses default white color with intensity of 10 and 0 falloff value.

The image below shows a quick render of the scene. As you can see, it still lacks something to give it realism. It lacks the impact's shockwave.

shockwave ring
Huge explosion often generate both energy and a sonic wave, known as a shockwave. This shockwave adds incredible realism and a sense of motion to the scene. To create a shockwave in the scene, a torus primitive is used.

The image below shows the place and size of the torus in the scene, the torus shockwave ring uses the same material as the bubble, see figure 5c.

Tip: You can add a multiple torii to create even stronger shockwave effects! Varying their diameters from smaller to larger as they get further from the bubble will often yields cool results.

To further enhance the shockwave effects, I added to the surrounding terrain area with waving clouds by using three squashed cylinders. Their placement is shown in the image on the left (the red color highlighted). The image on the right shows their materials in Material Editor.

And in the final render of the entire scene I added in some debris.

Tip: Debris adds a great deal of realism to the scene. Because my computer is not powerful enough to play with hundreds of terrain objects, I use primitive spheres to mimic a few pieces of debris in figure 9. However if you have a very powerful machine, you can try modeling debris with terrains and duplicate them into significant amount of wreckage and dispense them around the bubble and into the distance, varying size according to distance. This is left to your imagination. Now, let Bryce rocks!

If you have any comments, suggestions or question regarding this article, you can contact me through jykh@pc.jaring.my.


Jonathan Yuen Kok Hong is currently studying Computer Graphics discipline in Graphic Design Diploma in LimKokWing Institute of Creative Technology. He like Bryce, but always hopes it can be as stable as a chair. He can be contacted by email at jykh@pc.jaring.my.

[ galleries | archives | downloads | about | contacts ]
[ back to main page | back to contents page ]