If you declare a uniform that isn't used anywhere in your GLSL code the compiler will silently remove the variable from the compiled version which is the cause for several frustrating errors; keep this in mind!

Shaders are also very isolated programs in that they're not allowed to communicate with each other; the only communication they have is via their inputs and outputs.

Shaders always begin with a version declaration, followed by a list of input and output variables, uniforms and its main function. Each shader's entry point is at its main function where we process any input variables and output the results in its output variables

GLSL types

GLSL Vector Container A vector in GLSL is a 1,2,3 or 4 component container for any of the basic types just mentioned. They can take the following form (n represents the number of components)

Components of a vector can be accessed via vec.xwhere x is the first component of the vector. You can use .x, .y, .z and .w to access their first, second, third and fourth component respectively. GLSL also allows you to use rgba for colors or stpq for texture coordinates, accessing the same components.

The vector datatype allows for some interesting and flexible component selection called swizzling. Swizzling allows for the following syntax:

We can also pass vectors as arguments to different vector constructor calls, reducing the number of arguments required:

ins and outs Shaders are nice little programs on their own, but they are part of a whole and for that reason we want to have inputs and outputs on the individual shaders so that we can move stuff around. GLSL defined the in and out keywords specifically for that purpose.

ins and outs 2 Each shader can specify inputs and outputs using those keywords and wherever an output variable matches with an input variable of the next shader stage they're passed along. The vertex and fragment shader differ a bit though

If we want to send data from one shader to the other we'd have to declare an output in the sending shader and a similar input in the receiving shader. When the types and the names are equal on both sides OpenGL will link those variables together and then it is possible to send data between shaders

Uniforms Uniforms are another way to pass data from our application on the CPU to the shaders on the GPU

To declare a uniform in GLSL we simply add the uniform keyword to a shader with a type and a name. From that point on we can use the newly declared uniform in the shader. Let's see if this time we can set the color of the triangle via a uniform

.

I just don't believe you're capable of being an actor unless you have a desire to experience your emotions in a public way.

Possibly because I did start off as a journalist, my starting point has always been that you've got to keep an audience with you. Whatever you're doing, you always want a script to be a page-turner. It's very important never, ever, to feel above that.

Not looking for excuses is the right thing to do. I have made a lot of mistakes, and I still make mistakes, but I am not ashamed to look for the reasons behind those mistakes.

Unlike my opponent, I will not let oil companies write this country's energy plan, or endanger our coastlines, or collect another $4 billion in corporate welfare from our taxpayers.

If the 1992 and 2000 elections were any guide, third-party candidates are death on the mainstream parties with which they're most naturally aligned.

I don't mind anybody coming after me as long as they're coming with facts.

I'm too old to be a yuppie.

Gabby Giffords was a mentor of mine in the state Legislature and also in Congress.

Nothing in baseball can bring me down to the level where I was growing up in Pine Bluff, crying and broke. This is fun for me. Whenever you see me slumping, nah, I don't get upset; I'm all right.

I honestly believe that TV generally is obsessed with the ratings battle to the point of cutting its own throat.

People are almost always better than their neighbors think they are.

Ultimately, if I'm really moved by something, it's going to go on the record and that's that.

Authority could derive from passion, not pieces of paper.

Ending poverty calls for humility, honesty, freedom from ideology and refusal to accept cruel simplicities about anyone's human potential. It requires listening to the wisdom and cutting the nonsense from both the Right and the Left.

People are realizing that color has no bearing on whats known as brotherhood.

I've often had people ask me, would you allow a homosexual to be your friend. Yes, I will. And the reason I will is because I know that that person has problems, and if I can minister to those problems, I will.

Outside football, I just love life, you know. We're lucky to play football, to have all this body. Everyone's watching us. You see how many people, they come and watch the game. It's unbelievable, you see how many people they come. They shout your name and just enjoy life.

Through their work with fetal tissue, researchers hope to find ways to harness embryonic stem cells which have the ability to become any type of human cell and could provide new treatments for many illnesses.

I. Hate. Excuses. Excuses are a disease.

Life isn't fair. It's just fairer than death, that's all.

The biggest message I have for young women is, Don't start cutting off branches of your career tree unnecessarily early. Sometimes women say, I know I want to have a family or play in the local symphony, and they start pulling themselves out of their career path. You don't have to take yourself out of the running before you even start.

It has to be a very specific role for me because of my accent. I can't complain; I've been working since I got to LA. But it is hard. I have no training as an actress so I try whatever I do like school, because I'm learning.

It sounds so negative of me to say, but I don't feel like there were many coming-of-age films when I was growing up. I think that when I was a teenager, I felt really misrepresented in the teenage roles that I was watching onscreen. Especially in women.

I didn't take anything from anyone - first of all. Second of all, I opened a comedy club with money that I saved over 25 years. I created jobs.