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The Amiga-Video Journal June 1991 vol 2 issue 3 3D MODELING -"Earth Rise" - An Imagine Project by R.L. Kellogg, PhD Creating an animation of the rotating earth as seen from the moon was inspired by the incredible animation graphics of the PBS series "The Astronomers". Since the Amiga can also produce quality graphics and animation, I decided to create my own space art. The approach was conceptually simple: digitize a map of the earth and, using a 3D rendering program, wrap the image around a wireframe sphere. I would do the same thing again, creating an "atmosphere" of clouds for an extra effect. A digital "stage" could be set, hanging the rotating earth in a background of stars and filling the foreground with an image of lunar terrain. Step 1: Obtaining the Earth Map All of the maps of the earth in atlases, back issues of the National Geographic and airline travel magazines had too much printing and lettering. Fortunately, I found one map of the world that was simply an outline of continents. It was an easy matter using Digi-View (by NewTek) to digitize the map as a high resolution (640 x 400) image in "Line" mode, creating a 2-color map in only black and white. By adjusting the brightness control, I found a setting which clearly showed the continents. With DeluxePaint-III (by Electronic Arts) set to the HiRes 16- color mode, I loaded the 2-color map into the 16-color palette. I then adjusted the palette to provide a range of pastel colors for drawing yellow-tan deserts, brown mountain ranges, flat-green forests, and deep blue oceans. To insure that I only drew inside the continental boundries, I locked the blue ocean color with the "make stencil" command. This prevented any of my drawing from altering the ocean. Then for several hours I drew deserts, mountains, and forests, using National Geographic and several other atlases as a guide. Whenever I was able to make a feature that I liked, I used the brush command to replicate it. Mountain chains were easy that way! Sometimes I rotated and scaled (using the perspective) the brush to "fit" the geography. Every 15 minutes or so I would save my map to disk, in case of catastrophic failure. In an evening I had my artwork finished. Step 2: The Cloud Layer I wanted clouds over my earth to add some realism. In fact, I wanted the clouds as a separate layer just hovering over the earth. This meant that I needed to draw clouds which registered to the map that I had draw, but could be separated as a different rendering layer. Deluxe Paint III has a way of dealing with separate layers: it has a "fix" command to lock the screen image into an uneditable background. This command allows any new art work to be created on a separate foreground image plane while the background is still visible. I locked the finished earth map into the background and used the airbrush tool to spray on some white pixels to represent clouds. Then, I picked up those pixels as a series of small brushes and painted the clouds over the map. The polar regions were done in solid white, while desert areas were left untouched. I put clouds along the western edges of mountain chains and a tropical depression in the Indian Ocean. Short jerky motions with the mouse seemed to give the best "cloud effect", and I changed my brush often. Once finished, the entire cloud layer was transfered as a large brush to the alternate DP- III screen. Then, with the screen format requester, I collapsed the number of colors from 16 back to 2 and saved the cloud image, which now consisted of only white clouds and color zero background. For proper use in the 3D rendering program, I needed the colors reversed. I used the image utility Butcher (by Eagle Tree) to exchange the pixel order in the color registers and make the image a "negative" color. The final saved image was therefore made of black color zero clouds and white background. Step 3: Imagine God may have created the heaven and earth in six days, but to learn how to create images using Impulse's 3D rendering program "Imagine" takes considerably longer. But the effort is worth it, and after you get to know the program commands, Imagine becomes a very powerful 3D rendering program. First, I established a new project on disk df0: called "EarthAnim", and from the project screen made a new sub-project to hold the selected image renditions. The subproject was titled "EarthRise-Ham", and on initializing Imagine requests rendering information of rendering method, screen type, and path. EarthRise-Ham Rendering: Trace Picture: 320 x 400 Aspect 12:7 Image File: ILBM-12 bit Ham-yes Hires-no Lace-yes Image Path: df0:Im_Pix/Ham Anim Path: hd0:EarthAnim ILBM Trace was chosen to correctly render the earth's semi-transparent atmosphere. The picture size and aspect were from Imagine's preset list for HAM display. The image file type, ILBM-12, was chosen to allow other HAM programs such as Digi-Paint (by New Tek) and the Art Department (by ASDG). The complete animation will not fit onto floppy disk, since each HAM image is about 40K bytes. In the next article, I'll discuss how to compress the animation in HiRes format to a file of about 900K bytes. Step 4: Creating the Earth The basic work of creating the earth and the lunar foreground is done in Imagine's Detail Editor. In each case an IFF image is wrapped onto a geometric shape. For the earth, it is a sphere. For the moon, it is a vertical plane. To start the formation of the earth, I chose "Add Sphere" from the Function Menu. In the viewing windows (called "quads") a small, orange circle appears, and in the perspective window a small wireframe globe appears. Moving the mouse to either the front, side, or top viewing quads and clicking on the center of the orange circle (the axis origin), I change the circle color to blue. Only when the object is blue, that is "pick/selected", can I manipulate, move, or transform it. Rather than use the interactive transformations, I needed a precise change in scale for this sphere. From the Object Menu, I select "Transformation" and a requestor appears. Within the transformation requestor I select size and set each x,y, and z axis to 100 units, and "Perform" the transformation. A large multifaceted sphere now greets me in the quad and perspective views. In summary, the transformation I performed was: Earth Sphere Transformation Properties size xyz= 100 100 100 position xyz= 0 0 0 Step 4: Managing the Attributes This is by far the most challenging step. Not only must intrinsic color and texture properties be assigned to the budding earth sphere, but the extrinsic properties of the earth from the map image must be managed as well. With the earth sphere "pick/selected" (blue mode), I click on "attributes" of the Object menu. The following intrinsic properties were assigned: Earth Sphere Attribute Properties name: Earth color: 255/255/255 dither: 255 reflect: 0/0/0 hardness: 5 filter: 0/0/0 specular: 100/125/175 index refraction: 1.00 The specular color is essentially a blue-white highlight, which with the low value for hardness, will create a reflection highlight with a broad diffuse area. For this kind of an object, fairly high dithering is required to prevent "zoning" or "steps" in the color gradients of the final rendering. Special care must be taken with the earth map to insure that it wraps correctly around the sphere as a "brush attribute". The method is slightly different for a "wrap" that for a "flat" transfer. For the map, I wanted to wrap it around the sphere's z-axis. Therefore, clicking on the Brush-1 "brush attribute" box, the following extrinsic properties were assigned: Brush Attribute Properties brush name: df0:Im_Images/EarthMap-colormap.pic brush type: color wrap type: flat x wrap z The most difficult part of assigning the "brush attribute" is placing the brush axes onto the designated object. Since this is to be a "wrap", the z-axis of the brush needs to be near the z- axis of the object, the y-axis of the brush nearly non-existent, and the x-axis of the brush must extend slightly beyond the sphere's actual size. Within the "brush attributes" requestor, I chose the "transform" axis option to precise set the earth map axes: Brush Attribute Axis Transformation Properties size xyz= 110 4 300 position xyz= 0 -2 -150 The x-axis was made slightly larger than the 100-unit earth sphere. The y-axis of the brush is nearly non existent. However, the brush y-axis position at -2 is very important, since the it needs to be ever so slightly to the left of the object axis. The z-axis of the brush is used for scaling the image, and the map is stretched upward depending upon the size of z. The position of the z-axis at -150 (that is, one half of 300) insures image symmetry with respect to the earth's equator. After "performing" the axes transformations, I always like to make a visual check. Still within the "brush attribute" requestor, I click on the "edit" option which allows interactive positioning (move, using the "m" key) or scaling (size, using the "s" key) or rotating (using the "r" key). A yellow set of axes appears over the earth sphere, showing the brush axes inside a rectangle. From the front view, the upper right quadrant of the axes rectangle should cover the right half of the sphere. In the top view, the axes rectangle should look like a long, thin box going horizontally through the middle of the sphere. Everything correct, I tap the "spacebar" and exit the "brush transformation" requestor and "brush attribute" requestors. The earth sphere is saved as df0:Objects/earth.obj. I use a convention of naming objects ".wire" if it is just a wireframe object or ".obj" if I've attached attributes. Step 5: An Onion Skin Atmosphere Clearing the Detail Editor, I created another wireframe sphere to hold the cloud image in a manner similar to the earth. However, the wireframe sphere will be slightly larger than the earth, for in the next step will slip over the earth just like a layer of onion skin. Therefore the size of the "Add Sphere" was 105 units in x,y, and z. Clouds Sphere Transformation Properties size xyz= 105 105 105 position xyz= 0 0 0 The following intrinsic properties were assigned in the "attribute" requestor: Clouds Sphere Attribute Properties name: Earth-Clouds color: 255/255/255 dither: 255 reflect: 0/0/0 hardness: 10 filter: 0/0/0 specular: 110/110/110 index refraction 1.4 The atmosphere is made slightly harder that the earth beneath, and the index of refraction is set to 1.4. The index of refraction gives an exaggerated sense of depth between the earth and the clouds. Experimenting with the index of refraction can have some very exciting effects, especially if the earth and clouds are viewed from the night side. A glittering halo effect can be produced. The extrinsic properties of the clouds again come from a "brush" picture, but this time I use a "filter" brush rather than a "color" brush, to create a transparent atmosphere. Transparent, that is, except were color zero exists, which will reflect light just as real clouds. Brush Attribute Properties brush name: df0:Im_Images/EarthMap-clouds.pic brush type: filter wrap type: flat x wrap z The same kind of wrapping technique is used, but the brush axes are slightly larger to cover the larger wireframe sphere: Brush Attribute Axis Transformation Properties size xyz= 110 4 300 position xyz= 0 -2 -150 Step 6: The Earth-Clouds Group The earth and atmosphere spheres with their attributes were saved separately as earth.obj and clouds.obj. Then, still in Imagine's Detail Editor, I load both objects at once and use the "Pick All" command from the Pick/Select Menu. With them both "picked",I grouped together using the "Group" command from the Object Menu. Both objects are now bright blue. This combine group of two spheres is saved as df0:Im_Objects/earth.grp. Now I can treat "earth.grp" as a single entity and think of it simply as the object "earth-clouds". Step 7: The Moon Picture Although Imagine offers 3D rendering of terrain (or importing terrain from programs such as Vista by Virtual Reality), I had a terrific 2D HiRes image of the lunar horizon from Apollo 15 (which conincidentally is available from Virtual Reality). I wanted to use this image as a foreground "prop" on my 3D rendering stage. Therefore, in the Detail Editor I created a rectangular plane and pasted the picture of the moon onto it. To do this, I clicked on "Add Primitive" from the Function Menu and selected "Plane" within the Primitive Types Requestor. I created a plane with the following parameters: Plane Parameters: 200 width 50 height 5 horizontal sections 5 vertical sections After "pick/selecting" the plane, I attached the image of the moon horizon as a brush attribute: Plane Attribute Properties name: Moon color: 255/255/255 dither: 230 reflect: 0/0/0 hardness: 0 filter: 0/0/0 specular: 0/0/0 index refraction 1.0 Brush Attribute Properties brush name: df0:Im_Images/MoonHorizon.pic brush type: color wrap type: flat x flat z Since I just want to "paste" my moon picture onto this rectangular plane, the "wrap type" for both x and z was chosen as "flat-wrap". This means that the moon brush axes must have an origin just to outside the lower left-hand corner of the wireframe plane. The result was: Brush Attribute Axis size xyz= 404 4 250 position xyz= -202 -2 -52 The x-axis was scaled to be just as long (wide) as the rectangle, and the z-axis about five times higher. The z-axis scale was done by trial and error to fit the moon horizon image into pleasant proportions onto the rectangular frame. The finished object with attributes was saved as df0:Im_Objects/moon.obj. Step 8: Actors Upon a Stage The metaphor of a "stage" in 3D rendering is very appropriate: the camera, objects, lightsources, etc. become actors which are positioned, moved or changed according to a director's script. Within Imagine's Stage Editor, the interactive stage is represented by the quad viewing windows and the director's script is represented by a frame to frame sequencer accessible from the "Action" command of the Object Menu. The following sequence prepared my stage for 64 frames of the rotating earth. I worked between the "Action" director and the interactive Stage Editor to position and align my objects. However, for this tutorial, all of the setup work can be done directly within the "Action" director. Step 9: Action, Action Clicking on "Action" in the Stage Editor's Object Menu, I enter the "Action" director screen. "Action" commands are selected at the top of the screen in command boxes. Going left to right across the screen are the frame numbers (with initially only one frame), and scrolling down the screen are the actors. Initially there are only two actors, "camera" and "global" (really a "stage hand" who represents global stage settings). Additional actors are inserted at the line called "new". Each actor has settings of "actor" name, "position", and "alignment". I'll ignore "hinge" and "F/X" (special effects) until another tutorial. a) I first click on the Highest Frame Number and change it from 1 to 64. Across the "Action" field, the frame numbers 1 to 64 appear. b) I add my cast of characters one at a time using the "Add" command. The first object I add is the earth. At the line of "new" object, at the intersection of "frame 1" and "actor" I click the mouse. Imagine expects two mouse clicks in the add mode: one for the starting frame and one for the ending frame. With my first click at frame 1 the "add" command becomes hatched. Then, using the scrolling bar, I find the intersection of "frame 64" and "actor". I click again. A red bar appears and fills the actor line from frames 1-64. Then a requestor asks for the kind of object I'm adding. The earth is a "normal object", which on the next requestor I identify by filename as df0:Im_Objects/earth.grp. No cycling or transitioning effects are required. Within the "Action" screen, the "new" actor is now automatically chrisened "Earth-Clouds", derived from earth.grp's attributes. c) I repeat this procedure, adding into frames 1-64 the new actor object df0:Im_Objects/moon.obj. It appears within the "Action" screen as actor "Moon". d) I add another new actor into frames 1-64, but the type object is "Light Source". At the requestor, I define it as a spherical light with full intensity of 255/255/255. Its stage name automatically becomes "Lightsource". e) I add a second spherical lightsource into frames 1-64, but click the requestor boxes for "Cast Shadows" and "Diminish Intensity". Full intensity is set at RGB of 200/200/200. Its stage name becomes "Lightsource.1" f) I add a final object into frames 1-64, but its type is simply "Axis". Its stage name automatically becomes "Track". Step 10: More Action Now, I switch back in the "Info" mode of the "Action" director. If I stopped here and went back to the Stage Editor, I'd find all my objects piled up on top of each other at the stage position xyz= 0,0,0. Therefore, I must move the actors to their proper positions. The earth will be "upstage" and slightly to the left. The camera will be a considerable distance "downstage". In the camera's foreground will be the rectangle holding the moon's horizon. Illumination for the earth will come from LightSource off to the right, giving the illusion of a gibbous earth. My other light, Lightsource.1 will closely illuminate the picture of the moon. Not wanting two "suns" to illuminate the earth, this light must be placed such that the moon picture blocks any of its light and only casts a shadow onto the earth. (That's the reason for it's "cast shadow" mode). Lastly, the Track axis will left at xyz= 0,0,0 as an object for the camera to point at. Remaining within the "Action" direction, and using the "Info" mode, I click on each of the actor's green "position" bar at frame 1 and change positions: a) Camera: xyz = 0 -1000 0 b) Earth-Clouds xyz = -50 400 100 c) Moon xyz = 0 -320 -80 d) LightSource xyz = 1000 -250 100 e) LightSource.1 xyz = 0 -600 -150 f) Track xyz = 0 0 0 Step 11: Point and Twist I'm almost done setting the stage. However, three of the actors need special attention while in the "Action" director: a) Camera: I delete the blue "align" bar at frame 1, switch to the "add" command and double click on the camera's frame 1 align. A requestor appears asking whether to Tween, Align or Track. I select "Track" and at the next requestor, inform Imagine that the camera should follow the Object Name "Track". No camera rotation is required. b) Earth-Clouds: I delete the blue "align" bar at frame 1, switch to the "add" command and click once on Earth-Clouds frame 1 align and then once on frame 32. To make the earth appear in different perspective rotations, I select "Tween" and at the next requestor inform Imagine that it must change the alignment in between frames 1-32 by z = 180 (degrees). This will sequentially rotate the earth over 32 frames from its inital alignment to half way around. I repeat this procedure, clicking once on frame 33's align and then once on frame 64. I select "Tween" again, but set the z axis of rotation to 360. This finishes the task of rotating the earth. Imagine's logic compensates for looping, so although frame 64 ends up exactly at 360 (zero) degrees rotation, frame 1 actually is adjusted to start at 5.625 (360/64) degrees. c) Global: Using the "Info" command, I click on the red "actor" bar at frame 1. The only global property I need to change is "Star Density" for the number of background stars which Imagine will automatically generate. A star density of .01 looks nice. I exit the "Action" director by clicking "Done" Step 12: What Does The Stage Look Like Within the interactive Stage Editor, I select from the Display Menu "Camera View". If I've done everything correctly in the "Action" director, the perspective view should show a wireframe earth slightly above and to the left of center. The bottom half of the view should be covered by the moon-plane's rectangular mesh. If everything appears to be in its proper position, I select "Last Frame" from the Frame Menu" and check again. In creating animations sometimes I managed to lose my actors. If an actor is missing, I return to the "Action" director and check that the actor's line goes completely between frame 1 and 64 (camera and global are the exception). Before leaving the Stage Editor, I "Save Changes" from the Project Menu. I've forgotten to do this more than once, and it is very disheartening to lose the results of all this stage planning. Step 13: Rendering. In the Project Editor, I alway render one test frame before rendering the entire set of images. At 10 minutes per image (on a 28 MHz machine), that's a little over 10 hours for a 64 frame animation. Therefore, caution is warranted. I select frame 14 and click on "Generate". When complete, an asterick (*) appears below frame 1. Now comes the moment of truth. With frame 14 still selected, I click on "Show". Moments later I'm seeing a HAM image of the earth rising above the moon's horizon. By my subproject specification, this picture was automatically stored as df0:Im_Pix/Ham/pic.0014. The directory path to a floppy disk is inadequate for holding the complete animation. I can check my animation directory path for this subproject clicking on the "Modify" box of the Project Editor. Large frame renderings can be only done on a path to hard disk. My selected directory path is hd0:EarthAnim. Confident of my results, I select the range of frames 1-64 and click "Generate". See you in the morning! If you would like a disc containing a copy of the earth map, cloud layer and moon horizon images; the earth, clouds, and moon objects and the completed "Imagine" 3D rendering stage; and the completed rendering of frame #14 as Ham, HamE, HiRes, and ILBM-24 of this animation, send $5.00 to cover postage and handling to: First Principles Dr. Robert L. Kellogg 7509 Dew Wood Drive Rockville, MD 20855