HTML5 Canvas Library

shadowOnly Library Method

Short Description: Control display of shadows on transition

Signature: t.shadowOnly ([enable])
Group: Light and Shadow
Class: transition Class

If enabled (enable=true or missing) then only the shadows on the element are drawn, not the element itself. The idea is that the user makes sure that the element itself is drawn using HTML+CSS, while taccgl™ draws just the shadows on top of that.

opaqueShadow and shadowOnly are very similar. With shadowOnly still a texture must be given. Although the texture does not show up, transparent pixels in the texture define areaes where no shadows appear. In contrast opaqueShadow does not need a texture and makes the shadow appear on the complete element.

Note that in contrast to castShadow, which controlls the shadows casted by this transition on other transitions, opaqueShadow and shadowOnly control the shadows other elements or objects cast on this transition.

Using LightAmbDiff and lightBgAmbDiff the color of the shadow can be controlled.

The color and texture of the element becomes almost irrelevant, since only the shadow but not the element is drawn. The texture is however relevant in so far as no shadow is drawn where the texture is transparent while there is no or a transparent background color given. If on the other hand a non-transparent color is given, then shadows are shown throughout the animated element and the texture becomes completely irrelevant.

The first and second example below should show up nicely (although on slow GPUs shadows might be disabled completely and not show up). The second example needs far less texture space by using color instead of paint. The remaining examples study shadows casted from the image on the text leaving out shadows on the body for demonstration purposes.


The third example shows that shadowonly indeed just draws the shadow and nothing else. So the text does not show up only the shadow on the image on the text. In the forth example the text is displayed via HTML/CSS. While the image casts a shadow on it, it becomes slightly darker in displaying the shadow. In the last but one example the text has a background color and so the shadow appears solid. The last example shows disabeling shadows at all.

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