OpenGL::Array(3pm)

NAME
OpenGL::Array - Perl Array handling and conversion between Perl arrays and C array pointers.

SYNOPSIS
    use OpenGL qw(GL_FLOAT);

    my $array = OpenGL::Array->new(4, GL_FLOAT);
    my $c_ptr = $array->ptr(); # can be passed to OpenGL _c based functions
    $array->calc('col,27,+');
    my @val = $array->retrieve(0, 4);

DESCRIPTION
OpenGL::Array (OGA) objects provide Perl Array handling and conversion between Perl arrays and C array pointers.

Due to the difference between how Perl and C handle pointers, all Perl OpenGL (POGL) APIs that require pointers are suffixed with _c. OGAs provide a means to convert Perl arrays into C pointers that can be passed into these APIs.

Many POGL _c APIs also have a _s version to support SDL's packed string APIs; OGA provides APIs to convert between C arrays and packed strings.

POGL also provides many _p APIs that accept native Perl arrays, or in some cases OGAs directly. In the case of VBOs, OGAs may be bound to GPU buffers, automatically switching buffers at render time.

Note: Since OGAs are stored as typed C arrays, there is no conversion/copy/casting when passing them to POGL APIs, resulting in significant performance improvements over other non-compiled bindings (SDL, PyOpenGL, etc).

CREATING OpenGL::Array OBJECTS

"new"
        my $array = OpenGL::Array->new($count,@types);

    Creates an empty array object of $count rows made up data types @types.

"new_list"
        my $array = OpenGL::Array->new_list($type,@data);

    Creates and populates a uniform array object made up @data of type $type.

"new_pointer"
        my $array = OpenGL::Array->new_pointer($type,ptr,$elements);

    Creates an array object wrapper around a C pointer ptr of type $type and array length $elements. Caches C pointer directly; does not copy data.

    Note: because OpenGL::Arrays store to direct memory addresses, it is possible to assign to the array the pointer was obtained from and the results will be available in the array created by new_pointer - and vice versa (because they are viewing portions of the same memory).

"new_scalar"
        my $str = pack 'C*', 1 .. 255;
        my $array = OpenGL::Array->new_scalar(GL_UNSIGNED_BYTE, $str, length($str));

    Creates an array object from a perl scalar.

"new_from_pointer"
        my $array1 = OpenGL::Array->new_list(GL_UNSIGNED_BYTE, 1..9);
        my $array2 = OpenGL::Array->new_from_pointer($array1->ptr(), 9);

    Special case, creates a uniform GL_UNSIGNED_BYTE from a pointer.

USING OpenGL::Array OBJECT'S C POINTERS
OpenGL::Array objects are Perl references; in order to use them in OpenGL APIs that expect C pointers, you need to use the native pointer:

      my $array = OpenGL::Array->new(4, GL_INT);
      glGetIntegerv_c(GL_VIEWPORT, $array->ptr);
      my @viewport = $array->retrieve(0, 4);

OpenGL::Array ACCESSORS

"assign"
        $array->assign($pos, @data);

    Sets array data starting at element position $pos using @data.

"assign_data"
        $array->assign_data($pos, $data);

    Sets array data element position $pos using packed string $data.

"retrieve"
        my @data = $array->retrieve($pos, $len);

    Returns an array of $len elements from an array object.

"retrieve_data"
        my $data = $array->retrieve_data($pos, $len);

    Returns a packed string of length $len bytes from an array object.

"elements"
        my $count = $array->elements();

    Returns the element count from an array object.

"ptr"
        ptr = $array->ptr(); # typically passed to opengl _c functions

    Returns a C pointer to an array object.

    Returns a C pointer to an array object.

"offset"
        ptr = $array->offset($pos);

    Returns a C pointer to the $pos element of an array object.

"update_ptr"
        $array->update_pointer($ptr);

    Points the existing OpenGL::Array to a different data pointer.

BINDING TO VBOs
Helps abstract Vertex Array and VBO rendering.

# Requires GL_ARB_vertex_buffer_object extension and POGL 0.55_01 or newer

"bind"
        $array->bind($id);

    Binds a GPU buffer to an array object. If bound, glXxxPointer_p APIs will call glBindBufferARB.

"bound"
        my $id = $array->bound();

    Return bound buffer ID, or 0 if not bound.

AFFINE TRANSFORMS ON OpenGL::Array OBJECTS
Eventually, this API will abstract CPU vs GPU-based affine transforms for the best performance.

"affine"
        $array->affine($xform);

        # $xform is an NxN OpenGL::Array object used to transform $array.

        #N must be one element wider than the width of the array.

Calc: POPULATING AND MANIPULATING OpenGL::Array OBJECTS

"calc"
    Used to populate or mathematically modify an POGL array. Uses Reverse Polish Notation (RPN) for mathematical operations. At the moment, any array used with calc must be made of only of GL_FLOAT types.

        $array->calc($value);

    Populates the array with $value.

        $array->calc(@values);

    Populates each row of the array with @values, assuming rows have the same width as the length of @values. If the number of passed values must be evenly divisible by the number of elements in the array. The number of values becomes the number of "columns." The number of "rows" is the total number of elements of the array divided by the columns.

        $array->calc(1.0, '3,*', '2,*,rand,+', '');

    Resets the first column of each row to 1.0; multiplies the values in the second column by 3; multiplies the third column by 2, then adds a random number between 0 and 1; leaves the fourth column alone. During this particular calc operation there would be 4 columns.

    "calc" maintains a push/pop stack and a "register" for each column.

    "calc" also allows for other OpenGL::Arrays to be passed in. If multiple arrays are passed they must all have the same number of elements. Only the calling array will be operated on, but as each element is visited, the values from the other arrays are pre-added to the stack (in reverse order).

        $array->calc($array2, $array3, $array4, @values);

    calc currently supports the following primitives:

    "!" Logical "Not" for End of Stack (S0) for the current column; becomes 1.0 if empty or 0. otherwise 1.0

    "-" Arithmetic Negation of S0

    "+" Add S0 and Next on Stack (S1), pop operands and push result (Result)

    "*" Multiply S0 and S1; Result

    "/" Divide S1 by S0; Result

    "%" S1 Modulus S0; Result

    "=" Test S0 equality to S1; pop operands and push non-zero (1.0) for true, otherwise 0.0 (Boolean)

    ">" Test if S0 Greater than S1; Boolean

    "<" Test if S0 Lesser than S1; Boolean

    "?" If S0 is true (non-zero), pop S0 and S1; otherwise pop s0-3, push s1

    "pop"
        Pop s0

    "rand"
        Push a random number from 0.0 to 1.0

    "dup"
        Push a copy of S0

    "swap"
        Swap values of S0 and S1

    "set"
        Copy S0 to the column's Register

    "get"
        Push the column's Register onto the column's Stack

    "store"
        Pop S0, and copy the values from the matching row of the passed OpenGL::Array at that index. Values are copied into the current column registers.

          my $o1 = OpenGL::Array->new_list(GL_FLOAT, 1, 2, 3,  4, 5, 6);
          my $o2 = OpenGL::Array->new_list(GL_FLOAT, 7, 8 ,9,  10, 11, 12);
          $o1->calc($o2, "1,store,get","","get");
          $o1->retreive(0,6) will be (7, 2, 9,  10, 5, 12)

    "load"
        Pop S0, and set the values of the matching row of the passed OpenGL::Array named at that index. Values are copied from the current column registers.

          my $o1 = OpenGL::Array->new_list(GL_FLOAT, 1, 2, 3,  4, 5, 6);
          my $o2 = OpenGL::Array->new_list(GL_FLOAT, 7, 8 ,9,  10, 11, 12);
          $o1->calc($o2, "set","", "set,1,load");
          $o2->retreive(0,6) will be (1, 0, 3,  5, 0, 6)

    "colget"
        Pop S0, and push the column S0 value onto the current stack.

           $o = OpenGL::Array->new_list(GL_FLOAT, 1, 2, 3,  4, 5, 6);
           $o->calc('2,colget','','');
           # $o->retreive(0,6) will be (3, 2, 3, 6, 5, 6)

    "colset"
        Pop S0, and set the column S0 value to the new top of the stack.

           $o = OpenGL::Array->new_list(GL_FLOAT, 1, 2, 3,  4, 5, 6);
           $o->calc('27,2,colset','','');
           # $o->retreive(0,6) will be (1, 2, 27,  4, 5, 27)

    "rowget"
        Pop S0 and S1, and push the column S0 value from row S1 onto the current stack.

           $o = OpenGL::Array->new_list(GL_FLOAT, 1, 2, 3,  4, 5, 6);
           $o->calc('1,2,rowget','','');
           # $o->retreive(0,6) equiv (6, 2, 3,  6, 5, 6)

    "rowset"
        Pop S0 and S1, and set the column S0 value of row S1 to the new top of the stack.

           $o = OpenGL::Array->new_list(GL_FLOAT, 1, 2, 3,  4, 5, 6);
           $o->calc('27,1,2,rowset','','');
           # $o->retreive(0,6) will be (1, 2, 3,  4, 5, 27)

    "end"
        End processing; column unchanged

    "endif"
        Pop S0, End if true; column unchanged

    "endrow"
        End processing of current row; column unchanged

    "endrowif"
        Pop S0, End processing of current row if true; column unchanged

    "return"
        End processing; column value set to s0

    "returnif"
        Pop S0, End if true; column value set to s0

    "returnrow"
        End processing of current row; column value set to s0

    "returnrowif"
        Pop S0, End processing of current row if true; column value set to s0

    "if"
        alias to "?"

    "or"
        alias to "+"

    "and"
        alias to "*"

    "inc"
        Add 1 to S0

    "dec"
        Subtract 1 from S0

    "sum"
        Add and pop everything in stack; push result

    "avg"
        Average and pop everything in stack; push result

    "abs"
        Replace S0 with its absolute value

    "power"
        Raise S1 to the power of S0; Result

    "min"
        The lower of S0 and S1; Result

    "max"
        The higher of S0 and S1; Result

    "sin"
        Sine of S0 in Radians; Result

    "cos"
        Cosine of S0; Result

    "tan"
        Tangent of S0; Result

    "atan2"
        ArcTangent of S1 over s0; Result

    "count"
        Push the number of elements in the array

    "index"
        Push the current element index (zero-based)

    "columns"
        Push the number of columns in the array

    "column"
        Push the current column index

    "rows"
        Push the number of rows in the array

    "row"
        Push the current row index

    "pi"
        Push the the value of PI (but remember calc is just for floats)

    "dump"
        Print a dump of the current stack to standard out.

            OpenGL::Array->new_list(GL_FLOAT,7)->calc("dup,dec,2,swap,10,4,set,dump");

        Would print:

            -----------------(row: 0, col: 0)----
            Register: 4.0000000
            Stack  4: 7.0000000
            Stack  3: 2.0000000
            Stack  2: 6.0000000
            Stack  1: 10.0000000
            Stack  0: 4.0000000

AUTHOR
Bulk of documentation taken from http://graphcomp.com/pogl.cgi?v=0111s3p1&r=s3p6

Additions by Paul Seamons