Shadow study using direct light with Daylight system issue

[ctasker]

Hi all

Having a problem creating a shadow analysis in Viz 4. I need to produce shadow casting images for 24 different times (12 existing 12 proposed) and planned to use the daylight system but want to use it with only a direct light and raytraced shadows i.e. disable radiosity and skylight etc to have fast render times and clean shadow lines.

 

I've inserted the daylight system. I've opened the Assembly and turned off skylight and changed the sunlight to a standard light. I've turned off Radiosity in the Radiosity dialog and turned off exposure control in the environment dialog. set up the location and time.

When i try to render i get a completely washed out image with no shadows, all i can see is a white square where my ground plane object is. I cannot override the multiplier for the direct light which is set to 48.

 

Anybody know how to get my shadows to render properly or at all for that matter? What am i missing out on?

Hope somebody can help.

Thanks

[arkitekten]

Try turning the exposure contol back on (set it to logaritmic control), and place a 'V' in the 'exterior dayligt' setting of the exposure control box.

 

Keep the sunlight as a IES sun (the default when you make a daylight system).

 

You cannot override the multiplyer, when you have the sun as a 'geograftical location'. If you want to change it manually you need to 'V' the 'manual override' in the suns Control parameters.

 

Why do you turn off the skylight?

 

To get a good exterior picture, try doing the stuff i mentioned above (exposure control), don't manual override the sun, turn on the skylight, and turn on 'cast shadows' for the skylight.

 

This will normally produce fine resaults.

 

If not, try posting your picture, and dislog box setting in picture form - it makes it so mutch easyer to get a good overview for.

 

Hope it helps

 

Allan

[oluv]

another suggestion would be to turn off both sun and sky and place a further directional light with the same position and target as the sun, and then link the directional light to the sun system. it will chnage the position accoridingly...

[ctasker]

Hi Guys

thanks for replies,

Allan, i thought that the IES sun & sky only worked correctly with radiosity, i turned off those features because i needed fast render times and because i don't need subtle shadows. I did as you said and i'm getting an image with shadows but it is quite slow even at a low resolution. Any idea what is the purpose of including an option to change a sunlight into a standard light if it doesn't work?

 

I'm producing a shadow diagram effectively here where the primary concern is the sun's shadow locations at different times/dates specified by the planning authorities.

 

Oluv what is the bet way to link a direct light to a daylight system?

Might try this method with different shadow types and see if it makes any difference to render times.

[gfa2]

I've always just used the Sunlight system, instead of the Daylight system. The Sunlight system is basically just a direct light with overshoot turned on but it is tied to the Time and Location control parameters. Since it is a direct light you can use it with or without GI and it looks great. If you use it with the default scanline render use raytrace shadows for crisp lines or you can do shadow map for even faster renders, but fuzzier lines (although you can tweak those settings).

[upshot]

another suggestion would be to turn off both sun and sky and place a further directional light with the same position and target as the sun, and then link the directional light to the sun system. it will chnage the position accoridingly...

 

I do this all the time... I can't seem to ever get good results with the sun/sky tool but love to use the date/time position function of this tool...