Special Effects FX 스스로를 감동시켜야 최선을 다 한 것이다.

http://www.tokeru.com/mayawiki/index.php?title=Houdini

Special characters in path definition are:
	 @ - Typically expands to the HOUDINI_PATH. Thus, if the
			 HOUDINI_PATH was set to:
			 $HIP
			 $HFS/houdini
			 $HOME/houdini
			 a path defined as "@/vex" would expand to the paths
			 $HIP/vex
			 $HFS/houdini/vex
			 $HOME/houdini/vex
	 = - This expands to the $HIP variable. This path will always
			 point to where the currently loaded hip resides.
	 & - The ampersand character expands to the "default" path.
			 For example, to add a directory to the a path without
			 worrying about what the default path should actually be,
			 simply set the path to: "/mypath;&". This will search
			 the "/mypath" path first, then search the default path.
	 ^ - Some paths are used for multiple directories. For
			 example, the HOUDINI_VEX_PATH is used to define the
			 search path for Surface, Displacement, Sop, etc. VEX
			 shaders. For VEX, the ^ symbol expands to the shader
			 type. Thus, if the HOUDINI_VEX_PATH variable is set to
			 something like "/usr/local/vex;$HOME/vex/^", when
			 loading Surface shaders, the following directories will
			 be scanned:
			 /usr/local/vex
			 $HOME/vex/Surface
			 and if Sop shaders are being searched for, the
			 following paths will be searched:
			 /usr/local/vex

Houdini command-line Shell :  "hconfig -ap" 

수학 공식을 분해하여 Houdini에서 적용시키니 정말 이해가 잘 가고 좋다~!! 

 => length 

 => normalize

 => dot

 => dot

 => arccosine

맨 처음에는 viewoptrm `run("viewoptls")` 이렇게만 적용하였다.

그런데 문제가 실수로 한번만 툭 눌러도 view option들이 싸그리 지워지는 것이다. 

그래서 별 것 아니지만, 메시지를 띄어서 사용자가 선택할 수 있게하였고, 그 결과 값을 if문을 통해서 선택적으로 명령이 실행되게끔 코딩하였다. 

RenderMan Shader Compiles

The simplest way to get RenderMan shaders compiled and into Houdini is to do this:

% shader myshader.sl% 

rmands -l myshader.otl myshader.slo

This will create a digital asset with the compiled shader in it. Then you install thatthrough the file menu (File->Install Operator Type Library), and you're done - it willbe on the shader menu, with all of the UI elements already set up.

Even better, you can do this:

% rmands -l rmanshaders.otl *.slo

and this will put all your shaders into one asset. Then you can put this someplace like

$SHOW/houdini/otls

and set up Houdini with an environment variable, thus

HOUDINI_OTL_PATH = $SHOW/houdini/otls

Then whenever anyone runs Houdini, it will automatically load up all the shaders(and even better, the dialogs and other stuff).10

up x(cross) N    =>    X축.

N x(cross) X       =>    Y축.

N    =>    Z축.

후디니 내에서 쓸 수 있는 함수를 만들때의 기본 틀:

[return_type] functionName([[arg_type1] arg_name1 [, [arg_type2] arg_name2] ...])
{
...
}

반환형 타입과 인수 타입은 float,  string, vector, or matrix 를 쓸 수 있다.

#은 주석처리.

만약 반환형과 인수의 타입을 명시하지 않으면 후디니는 자료형에 float이 있는 것처럼 인식한다.
그리고, 만약 인수타입에 string을 넣어야 하는데 그것을 잊고 넣지않으면, float으로 인식해서 잠재적 버그를 
열심히 찾는다고 한다. 
자료형을 꼭 명시해야겠다.


Examples
# Function to find the minimum value of two
# floating point numbers

min(v1, v2) {
    if (v1 < v2) {
        return v1;
    } else {
        return v2;
    }
}

# Function to reverse the order of a string

string strreverse(string in) {
    float len = strlen(in);
    
    string result = "";
    
    for (src = len-1; src >= 0; src--) {
        result += in[src]; return result;
    }
}

# Example to find the minimum element in a vector

float vecmin(vector vec) {
    min = vec[0];
    
    for (i = 1; i < vsize(vec); i++) {
        if (vec[i] < min)  min = vec[i];
    }
    
    return min;
}

# Example to transform a vector into the space
# of an object passed in.

vector opxform(string oname, vector v) {
    matrix xform = 1;
    
    if (index(oname, "/obj/")) {
        xform = optransform(oname);
    } else {
        xform = optransform("/obj/"+oname);
    }
    
    return v * xform;
}

# Example to find all objects which have their
# display flag set

string opdisplay() {
    string objects = run("opls /obj");
    string result = "";
    nargs = argc(objects);
    
    for (i = 0; i < nargs; i++) {
        string obj = arg(objects, i);
        if ( index(run("opset " + obj), " -d on") >= 0 ) result += " " + obj;
    }
    
    return result;
}