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Tuesday, April 22, 2008

ocean shader


heres a crack at an ocean scene,
not happy with it yet...but its been interesting.

ill have to find a model to stick in the water...

i got a SSS pass in there but its hard to tell if it really working properly.

no white caps yet and no tru Zdepth yet - my dodgey ZDepth was made by using an edge detect on the alpha of the water essentially creating a horizon line then blurring this and adding it to itself for the desired effect.

this was used as a mask for desaturation and SSS as well as blur.

the spec is bloomed out as well...all comped in Houdini :)

edit: next time i might try and reduce the wave height in relation to zDepth to try and
fake the scale of the scene - like a perspective cheat...any ol' trick to reduce rendering times on my old box.

edit: looking at other peoples work - i realised
i can fake the distance with a flatten effect based on camera distance.

-----------------------
some more shader practice:
simple opacity
dont forget:
the RGB has to be multipled by the Alpha to get some black for the OPACITY.
in this example i had a 32 bit TGA - which i then broke into its RGB vector and a 4th float value (the alpha) with a convert VOP
(convert Vector4 to Vector)

an image with an alpha channel may need the 'premultiplied' treatment.
- this can be done in COPS.

Monday, April 21, 2008

weekly research: MIP mapping

what is MIP ?

wikipedia has the answers

Mip maps (invented by Lance Williams in 1983)

... are pre-calculated, optimised collections of bitmaps that accompany a main texture, intending on increasing rendering spped and reducing artifacts.

MIP is an acronym, from the latin : multum in parvo, or "much in a small space"

If the full res map isnt required - the renderer will automatically switch to a lower res version, or interpolate between the full- res version and a lower res version - if tri-linear filtering is enabled.

see anistropic mip mapping.

capsule asset re-made

the original capsule asset post (post #2 is updated with some pics)
and the asset was remade.

original capsule post

Wednesday, April 16, 2008

crab update !


HOOOPLA !
a new render of the crab with rangi's HDRI shader
there'll be more renders as his face design will be changing...

Saturday, April 12, 2008

ball ' o worms


this was supposed to be for CGSphere - but the camera is slightly off....so i think ill do it again in Houdini ! :D

changing the colours and saturation in photoshop on the worms pass really helped with the realism. I would like to improve the realism of the dirt.

Wednesday, April 9, 2008

LINUX file permissions


from www.linuxforums.org/security/file_permissions.html

r readable
w writable
x executable

u user
g group - ie Administrators
0 others - not a member of a group or the owner of the file
a all
- no permission

use ls -l to see file permissions

eg

ls -l myfile
-rwxr-x--- 1 george administrators 10 2006-03-09 21:31 myfile

so for george - the owner - the file is readable , writable and executable.
for other administrators - the file is only readable - not writable but still executable
other users cannot read, write or run this file.

changing permissions : chmod
if george wanted to give write permission tot he other administrators
he would type

chmod g+w myfile
see the url for details


tricks from the forums ! - thx to all Houdniks out there !


To detect holes, in non-manifold geometry, you can use the Divide SOPs 'Removed shared Edges' Toggle.

If this returns no points or prims, than your geo is solid. Otherwise you have non-manifold geometry, (either has holes, or some flipped prims and what not)

Tuesday, April 8, 2008

some HScript ! arc, argc

arg - looks really useful.

returns an argument - the one4 specified from a list of argts in a string

it fillows the format arg("stringline", float arg number - starting from 0)
ie
arg("yellow world ",1) returns world
arg("yellow world ",0) returns yellow


argc (arg-count) returns a number of arguments
eg
argc ("This string has eight words seperated by spaces") returns 8

argc ("Quoting `makes this one arg`") only returns 2 as `makes one arg` is only counted as one arg - because of the quotes.

Monday, April 7, 2008

weekly research ! some MATHS



Summation

reading some research on making car shaders i saw some crazy maths i recognised from high school so i was curious as to what it all meant.

from wikipedia
Summation
is the addition of a set of numbers; the result is their sum or total.


Vetcors

unlike scalars, vectors have more than one component.
they have a direction and a magnitude.

they can be notated with an arrow over the start point and the end point

there are a few methods for addition

a. the end to end method - move one vector to the end of the other one
b. parrallelogram method

in addition they are associative A+B = B + A

negative vectors (5:31)

Subtraction of vectors
A - B = C
A+(-B) = C
(the negative of a vector is pointing in the opposite direction)

when you add scalrs - there is only one answer
but with vectors there could be more than one answer if there is missing information
ie we dont know the direction of a vector - but we kow its magnitude.

with a 3D say vector A vector - we project it onto the xyz axes

the unit vector is like a control
the axes are always pointing in the positive direction
and the magnitiude is always 1 for each axis.
it is noted with little roofs on the vectors to show its a unit vector

decomposition of the vector A:
we break it down into its 3 components


the magnitude is the root of A2 + Y2 + Z2
it is notated with Abs lines / vertical bars around the A (magnitude is a scalar)

Multiplication
there are two methods
dot product / saclar product - notated with a fat dot

the angle method
we project B onto A - then the dot product is |A| |B| cos Theta
the dot product can be pos or neg or = to zero.

it doesnt matter if you take the acute angle of theta or the obtuse angle of theta
their cosines are the same

to be continued !

Tuesday, April 1, 2008

weekly research: CHROMATIC ABERRATION



from wikipedia:

chromatic aberration occurs when a lens has a slightly different refractive index for different wavelengths of light - resulting in some fringing of some colours.

...just like 'The Dark Side of the Moon' - :D
this could be and is often used to enhance realism in cg images.
how ?

here's my hack
we could render split the RGB and adjust the hue and offset or distort the channel a little then mix it back in the comp.

& here' s my attempt at a copnet - made long after this post : 22 Jan 2010 !




and here's a beautiful example from Andrew Schneider:

schneiderFX/Macro

UPDATE...
I've applied it a little here for my bubble render...hopefully it helps sell it a bit !



UPDATE #2

I stumbled across a link to a great tutorial for achieving the effect in After FX
by Cyril Kotecky on Jul 19, 2013
 
a couple of points I got from it:
the colors used in the effect in this tut were pure Cyan and Magenta

The other thing was that the effect was used more toward the boundary of the image - the effect was masked off in the center of the image with a soft-falloff / a large amount of feathering.

some new work - a CRAB


stay tuned for some renders !

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