I wonder how you control environnment colour such sun, sea, fog light colour etc etc as time pass My world sky, sea and sun object are controled by material (the terrain is lighted by d3d&normal) When sun rise or fall I must have nice colour change and I think more than controlling the colour with hard coding (eg: 255-time,255-time/whatewer,255+time/hurgh&blurg) To make an image with nice gradient of colour then grab on it the needed colour. saving&loading the structure containing those data will be done simply so one don''t need the image appart if a change is needed. (eg: if(existimageGradient()) { loadImageAndGrabGradient(); SaveGradientStructure(); } else LoadGradientStructure(); The avantage is that you have a visual control of the color change and changing gradient if ya don''t like can be done in a snap with photoshop for example. Also doing it programmatically would be complicated while I have also wheater color change (storm=darker)and there is a lot of object to colorize that will act independently: Sun: Material Sky: Material Fog: d3d Colour Sea: Material Light: d3d colour Notice that there will be a point each 30 sec and color beetween those point will be simply interpolated. (I think also to do the gradient only for period like 5h30 am/pm to 7h30 am/pm) I wonder how people commonly do this ? is your method simpler ? more flexible ? Dan