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3D model eclipse and script animation

Anonymous

3D model eclipse and script animation

Anonymous
No aplicable

Hi all,

 

I'm new here. Great product of which accuracy I was already aware. So I choose it to create this model.

 

I'am having big problems with lights. Initially I was thinking the better kind of light (for the sun) would be distant lights, since they don't decrease with distance. I tried all other kinds but I can't see the shadow of the moon on the earth when the moon cross the ecliptic (21 august).

I tried several objects closer to the earth and they do cast their shadows but more they walk away from earth less shadow is visible till it disappear way before reaching the real moon orbit.

 

Surely there is more than one setting that I missed. How can I solve this shadow problem? Is Autocad appropriate to render this type of model?

 

Thank you,

Valerio

 

P.S. I'm working on a script for this: is there a way to render the script animation (included shadows!)?

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john.vellek
Alumni
Alumni

HI @Anonymous,

 

This is an interesting problem. I think using the sun for lighting might still be the answer. The question is how you are setting up the location for the view to be shown.

 

My point is that if you are looking at the wrong side of the Earth then you won't see a shadow. Can you walk me through your process so I can try to help you with the lighting?


John Vellek


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leeminardi
Mentor
Mentor

I opened your file and place a wall between the moons and the earth, turned on your Distantlight5, set shadow type on and to Sharp and got no shadows for the moons.  Do not use shadow maps.  Usually if you want softer shadows you would turn on final gather and other global illumination effects.  These features do not make sense for celestial objects that are getting very little indirect lighting.

 

I then turned off Distantlight5 and added a new Distantlight1 that went from the sun (0,0,0) to the center of the earth.  As you can see the shadows do not fall in line with the direction from the sun to the earth but are transposed to the right. I am not sure why this is. 

 

 

r1.png

 

I do not think the problem you are having is due to the drop off of a distant light’s intensity.  There is no fall off that I can see.

 

The scale of your drawing is very large.  Although AutoCAD has a double precision data base (64 bit with 56 bit mantissa) I am not sure of the precision for rendering operations.

 

I suggest scaling the entire model so that the range of values is less than a million to one.  If you are trying to create a relistic image that should be good enough.  If you are doing astronomical calculations I suggest you look into another tool.

 

3DS Max has much better lighting feature but only a 32 bit data base.

 

I hope this helps.

 

~Lee

lee.minardi
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Anonymous
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Thank you,

 

I'm just learning and your feedback is important.

 

Few days ago I made some test video for a 24h script. The final point of view of the animation will be fixed on the earth during the eclipse, so the shadow of the moon will be visible.

 

I think should be a setup of light that can show this umbra.

 

Valerio

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Anonymous
No aplicable

Thank you,

 

I also experienced this shift-shadow problem having distant light set in the center of the sun. I think that distant light are only vectorial, I mean you can set a start point and a direction: all objects/surfaces (like one half of the sun) interact with the light.

 

I started this project with autocad because I knew its precision and the data source of this model are from official and ephemeris calculation, often precise till 8th decimal point. Don't know or used any other 3D software. I will give 3DS Max a try.

 

Valerio

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leeminardi
Mentor
Mentor

I did a quick mockup of an Earth, Moon and Sun (as a light source) in 3ds Max to see if I could get a shadow to move across the Earth.  I did not give much attention to the scale of things but did get some encouraging results.  I gave the Earth linear rotation (I did not bother with a tilt axis) and set the moon to travel along a arbitrary spline. See the attached animation for the way the shadow move across the Earth.  I did not have much luck using a standard light so I used the 3ds Max instead and positioned the object along the Sun vector. Depending upon your end goals Max may have some potential.

MoonShadow01.jpg

~Lee

lee.minardi

Anonymous
No aplicable

Thank you for hint.

 

The aim is create a 3D model (for the system sun-earth-moon) synchronized with the lunar phases during year.

Respecting data is mandatory. I tried to import the dwg in 3DS Max but it gone a mess. Perhaps is better re-start from scratch.

 

If maintaning the distances in 3DS Max let the moon cast its shadow, I must have miss something with lights in autocad hence I was hoping in a minor adjustment within autocad itself.

 

Valerio

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