2D Canvas Context
There are actually two things we refer to as 2D/3D in the context
of taccgl™. (1) First the final animation may be 2D or 3D, whereby 2D
means that all objects shown in the animation are in the z=0 plane,
all objects are flat and directly located on the screen. In contrast
there is 3D where the objects could conceptually be anywhere and are
mapped on the screen using a 3D perspective projection. In addition
the objects shown may not be flat but have a depth. As discussed
in Coordinate System taccgl™ does not really make a
difference here but always does everything in 3D. The user may
specify z-coordinate 0 and depth 0 and so just operate in 2D.
(2) The second important difference is 2d and 3d canvas
context. Canvas is the name of a new HTML 5 element used for
drawing. It provides multiple drawing contexts a 2d drawing context
and in some browsers a 3d context. [The 2d context is part of the HTML
5 standard and implemented in most of the current browser versions
while 3d context is not yet formally part of HTML 5; the standard just
says there may be one in the future. As far as we understand WebGL™ is
a standard that may or may not become the HTML canvas 3d context,
however, for now it is implemented in newer versions of Firefox,
Chrome, Safari, and also internet explorer since version 11. ] For
various reasons the 3d context may not be available, e.g. because it
is not activated in the browser, because the computers graphic card and
drivers do not support it.
taccgl™ will try to use the 3d context of HTML 5 canvas and in
many cases if it does not succeed try to fall back into using 2d
Although 2d context does not specifically
support 3D drawing it can still be used with restrictions (see below
Limitations of 2D Context) for 3D some animations as well.
Programming Portable Animations
To some extend the idea is that an animation works with 3d
context and 2d context as well, just its visual appearance and
performance might be different and elements that work in 3d only
just do not appear in 2d mode.
If a certain feature is not available
in 2d context, then its associated methods do not produce an
error but just do not show anything. Information retrieved
from taccgl™ in that situation might be not present or wrong and
cannot be relyed on.
Using the methods ddmode and dddmode
in ddmode you can detect the context used and program your
animation differently for both contexts. In case of a WebGL™ error
or if 3d mode just is too slow, taccgl™ might switch into 2d mode
while an animation is running.
It is always required to test your application in both 2d and 3d context
mode, because there may be errors that manifest only in one
of these modes.
Limitations of 2D Context:
We recommend to go through the documentation and the examples with
2d context to see the differences.
- There is no Lighting in 2D canvas. All lighting options are
- Some kind of parallel projection instead of perspective
projection is used. For deep objects or objects moving far away
from the z=0 plane this does not look correct, since objects do
not get smaller when moved away. However it is not a problem for
objects near the z=0 plane that are not very deep.
- The hidden line and hidden surface algorithms in the 2d context
are not very advanced. They can correctly display a cube but they can
not handle surfaces that cut through each other.
Sometimes the result can be improved by animating objects that are
further away first.
- There are no shaders and consequently no custom shaders available.
The class taccglShaderConfig Class does not work,
i.e. method calls do not produce an error but defined custom
shaders and options are ignored.
- taccglFlexiBorder Class is not supported i.e. some method calls
do not produce an error but also have no effect and so flexible elements
do not look flexible but just as ordinary transitions.
- taccgl3DObject Class is not supported i.e. method
calls work to some extend, but nothing will be shown on the
taccglOBJFile Class and taccglMTLFile Class
will not download anything.
It is a good idea to check ddmode / dddmode before using these classes,
although in many cases such a test is not necessary because the called methods still work to some extend
just that the taccgl3DObject Class 3DObjects, do not appear.
However, you can not rely on any information retrieved from these
classes since the model is not loaded.
- The hardware acceleration of 3D canvas is extremely fast when used
with a good graphics card. On the other hand the 2d canvas is
pretty fast as well and sufficient for many animations.
3d context provides many many more features that are currently not explicitly
supported by taccgl™ but may be in future versions.
WebGL™ is a trademark of the Khronos Group Inc.