OpenGL Shading Language</a>.
</p>
-<p>
-Last updated on 28 March 2007.
-</p>
-
<p>
Contents
</p>
<ul>
+<li><a href="#envvars">Environment variables</a>
+<li><a href="#120">GLSL 1.20 support</a>
<li><a href="#unsup">Unsupported Features</a>
<li><a href="#notes">Implementation Notes</a>
<li><a href="#hints">Programming Hints</a>
-<li><a href="#standalone">Stand-alone Compiler</a>
+<li><a href="#standalone">Stand-alone GLSL Compiler</a>
<li><a href="#implementation">Compiler Implementation</a>
<li><a href="#validation">Compiler Validation</a>
</ul>
+
+<a name="envvars">
+<h2>Environment Variables</h2>
+
+<p>
+The <b>MESA_GLSL</b> environment variable can be set to a comma-separated
+list of keywords to control some aspects of the GLSL compiler and shader
+execution. These are generally used for debugging.
+</p>
+<ul>
+<li>dump - print GLSL shader code to stdout at link time
+<li>log - log all GLSL shaders to files.
+ The filenames will be "shader_X.vert" or "shader_X.frag" where X
+ the shader ID.
+<li>nopt - disable compiler optimizations
+<li>opt - force compiler optimizations
+<li>uniform - print message to stdout when glUniform is called
+<li>nopvert - force vertex shaders to be a simple shader that just transforms
+ the vertex position with ftransform() and passes through the color and
+ texcoord[0] attributes.
+<li>nopfrag - force fragment shader to be a simple shader that passes
+ through the color attribute.
+<li>useprog - log glUseProgram calls to stderr
+</ul>
+<p>
+Example: export MESA_GLSL=dump,nopt
+</p>
+
+
+<a name="120">
+<h2>GLSL 1.20 support</h2>
+
+<p>
+GLSL version 1.20 is supported in Mesa 7.3 and later.
+Among the features/differences of GLSL 1.20 are:
+<ul>
+<li><code>mat2x3, mat2x4</code>, etc. types and functions
+<li><code>transpose(), outerProduct(), matrixCompMult()</code> functions
+(but untested)
+<li>precision qualifiers (lowp, mediump, highp)
+<li><code>invariant</code> qualifier
+<li><code>array.length()</code> method
+<li><code>float[5] a;</code> array syntax
+<li><code>centroid</code> qualifier
+<li>unsized array constructors
+<li>initializers for uniforms
+<li>const initializers calling built-in functions
+</ul>
+
+
+
<a name="unsup">
<h2>Unsupported Features</h2>
<p>
-The following features of the shading language are not yet supported
+The following features of the shading language are not yet fully supported
in Mesa:
</p>
<ul>
-<li>Dereferencing arrays with non-constant indexes
-<li>Comparison of user-defined structs
-<li>Linking of multiple shaders is not supported
+<li>Linking of multiple shaders does not always work. Currently, linking
+ is implemented through shader concatenation and re-compiling. This
+ doesn't always work because of some #pragma and preprocessor issues.
<li>gl_ClipVertex
+<li>The gl_Color and gl_SecondaryColor varying vars are interpolated
+ without perspective correction
</ul>
<p>
<li>The quality of generated code is pretty good, register usage is fair.
<li>Shader error detection and reporting of errors (InfoLog) is not
very good yet.
-<li>There are known memory leaks in the compiler.
<li>The ftransform() function doesn't necessarily match the results of
fixed-function transformation.
</ul>
<a name="standalone">
-<h2>Stand-alone Compiler</h2>
+<h2>Stand-alone GLSL Compiler</h2>
<p>
A unique stand-alone GLSL compiler driver has been added to Mesa.
</ul>
<p>
-To build the glslcompiler program (this will be improved someday):
+After building Mesa, the glslcompiler can be built by manually running:
</p>
<pre>
- cd src/mesa
- make libmesa.a
- cd drivers/glslcompiler
+ make realclean
+ make linux
+ cd src/mesa/drivers/glslcompiler
make
</pre>
emit GL_ARB_vertex_program-style instructions:
</p>
<pre>
- glslcompiler --arb --linenumbers --vs vertshader.txt
+ bin/glslcompiler --debug --numbers --fs progs/glsl/CH06-brick.frag.txt
</pre>
<p>
-The output may look similar to this:
+results in:
</p>
<pre>
-!!ARBvp1.0
- 0: MOV result.texcoord[0], vertex.texcoord[0];
- 1: DP4 temp0.x, state.matrix.mvp.row[0], vertex.position;
- 2: DP4 temp0.y, state.matrix.mvp.row[1], vertex.position;
- 3: DP4 temp0.z, state.matrix.mvp.row[2], vertex.position;
- 4: DP4 temp0.w, state.matrix.mvp.row[3], vertex.position;
- 5: MOV result.position, temp0;
- 6: END
+# Fragment Program/Shader
+ 0: RCP TEMP[4].x, UNIFORM[2].xxxx;
+ 1: RCP TEMP[4].y, UNIFORM[2].yyyy;
+ 2: MUL TEMP[3].xy, VARYING[0], TEMP[4];
+ 3: MOV TEMP[1], TEMP[3];
+ 4: MUL TEMP[0].w, TEMP[1].yyyy, CONST[4].xxxx;
+ 5: FRC TEMP[1].z, TEMP[0].wwww;
+ 6: SGT.C TEMP[0].w, TEMP[1].zzzz, CONST[4].xxxx;
+ 7: IF (NE.wwww); # (if false, goto 9);
+ 8: ADD TEMP[1].x, TEMP[1].xxxx, CONST[4].xxxx;
+ 9: ENDIF;
+ 10: FRC TEMP[1].xy, TEMP[1];
+ 11: SGT TEMP[2].xy, UNIFORM[3], TEMP[1];
+ 12: MUL TEMP[1].z, TEMP[2].xxxx, TEMP[2].yyyy;
+ 13: LRP TEMP[0], TEMP[1].zzzz, UNIFORM[0], UNIFORM[1];
+ 14: MUL TEMP[0].xyz, TEMP[0], VARYING[1].xxxx;
+ 15: MOV OUTPUT[0].xyz, TEMP[0];
+ 16: MOV OUTPUT[0].w, CONST[4].yyyy;
+ 17: END
</pre>
<p>
<h2>Compiler Validation</h2>
<p>
-A
new <a href="http://glean.sf.net" target="_parent">Glean</a> test has
+A <a href="http://glean.sf.net" target="_parent">Glean</a> test has
been create to exercise the GLSL compiler.
</p>
<p>
-The <em>glsl1</em> test runs over 130 sub-tests to check that the language
+The <em>glsl1</em> test runs over 170 sub-tests to check that the language
features and built-in functions work properly.
This test should be run frequently while working on the compiler to catch
regressions.
projects / mesa.git / blobdiff