int main(int argc, char **argv) {
FILE *fp = fopen(argv[1], "r");
if (fp == NULL) return 0;
dump_bmp(fp);
fclose(fp);
return 0;
}
void test_stencil(void)
{
GLint numStencilBits;
GLuint stencilValues[NumTests] = {
0x7, // Result of test 0
0x0, // Result of test 1
0x2, // Result of test 2
0xff // Result of test 3. We need to fill this value in a run-time
};
int i;
DEBUG_MSG("----------------------------------------------------------------");
RD_START("stencil", "");
ECHK(surface = eglCreatePbufferSurface(display, config, pbuffer_attribute_list));
ECHK(eglQuerySurface(display, surface, EGL_WIDTH, &width));
ECHK(eglQuerySurface(display, surface, EGL_HEIGHT, &height));
DEBUG_MSG("PBuffer: %dx%d", width, height);
/* connect the context to the surface */
ECHK(eglMakeCurrent(display, surface, surface, context));
GCHK(glFlush());
if (!program) {
program = get_program(vertex_shader_source, fragment_shader_source);
GCHK(glBindAttribLocation(program, 0, "aPosition"));
link_program(program);
/* now set up our uniform. */
GCHK(uniform_location = glGetUniformLocation(program, "uColor"));
}
GCHK(glClearColor(0.0, 0.0, 0.0, 0.0));
GCHK(glClearStencil(0x1));
GCHK(glClearDepthf(0.75));
GCHK(glEnable(GL_DEPTH_TEST));
GCHK(glEnable(GL_STENCIL_TEST));
// Set the viewport
GCHK(glViewport(0, 0, width, height));
// Clear the color, depth, and stencil buffers. At this
// point, the stencil buffer will be 0x1 for all pixels
GCHK(glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT));
// Use the program object
GCHK(glUseProgram(program));
// Load the vertex position
GCHK(glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, vVertices));
GCHK(glEnableVertexAttribArray(0));
// Test 0:
//
// Initialize upper-left region. In this case, the
// stencil-buffer values will be replaced because the
// stencil test for the rendered pixels will fail the
// stencil test, which is
//
// ref mask stencil mask
// ( 0x7 & 0x3 ) < ( 0x1 & 0x7 )
//
// The value in the stencil buffer for these pixels will
// be 0x7.
//
GCHK(glStencilFunc(GL_LESS, 0x7, 0x3));
GCHK(glStencilOp(GL_REPLACE, GL_DECR, GL_DECR));
GCHK(glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[0]));
// Test 1:
//
// Initialize the upper-right region. Here, we'll decrement
// the stencil-buffer values where the stencil test passes
// but the depth test fails. The stencil test is
//
// ref mask stencil mask
// ( 0x3 & 0x3 ) > ( 0x1 & 0x3 )
//
// but where the geometry fails the depth test. The
// stencil values for these pixels will be 0x0.
//
GCHK(glStencilFunc(GL_GREATER, 0x3, 0x3));
GCHK(glStencilOp(GL_KEEP, GL_DECR, GL_KEEP));
GCHK(glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[1]));
// Test 2:
//
// Initialize the lower-left region. Here we'll increment
// (with saturation) the stencil value where both the
// stencil and depth tests pass. The stencil test for
// these pixels will be
//
// ref mask stencil mask
// ( 0x1 & 0x3 ) == ( 0x1 & 0x3 )
//
// The stencil values for these pixels will be 0x2.
//
GCHK(glStencilFunc(GL_EQUAL, 0x1, 0x3));
GCHK(glStencilOp(GL_KEEP, GL_INCR, GL_INCR));
GCHK(glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[2]));
// Test 3:
//
// Finally, initialize the lower-right region. We'll invert
// the stencil value where the stencil tests fails. The
// stencil test for these pixels will be
//
// ref mask stencil mask
// ( 0x2 & 0x1 ) == ( 0x1 & 0x1 )
//
// The stencil value here will be set to ~((2^s-1) & 0x1),
// (with the 0x1 being from the stencil clear value),
// where 's' is the number of bits in the stencil buffer
//
GCHK(glStencilFunc(GL_EQUAL, 0x2, 0x1));
GCHK(glStencilOp(GL_INVERT, GL_KEEP, GL_KEEP));
GCHK(glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[3]));
// Since we don't know at compile time how many stencil bits are present,
// we'll query, and update the value correct value in the
// stencilValues arrays for the fourth tests. We'll use this value
// later in rendering.
GCHK(glGetIntegerv(GL_STENCIL_BITS, &numStencilBits));
stencilValues[3] = ~(((1 << numStencilBits) - 1) & 0x1) & 0xff;
// Use the stencil buffer for controlling where rendering will
// occur. We disable writing to the stencil buffer so we
// can test against them without modifying the values we
// generated.
GCHK(glStencilMask(0x0));
for (i = 0; i < NumTests; i++) {
GCHK(glStencilFunc(GL_EQUAL, stencilValues[i], 0xff));
GCHK(glUniform4fv(uniform_location, 1, colors[i]));
GCHK(glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices[4]));
}
ECHK(eglSwapBuffers(display, surface));
GCHK(glFlush());
ECHK(eglDestroySurface(display, surface));
GCHK(glFlush());
usleep(1000000);
dump_bmp(display, surface, "stencil.bmp");
RD_END();
}
