ios - OpenGL ES 2.0 - GL_POINTS and Stencil Buffer -

ios - OpenGL ES 2.0 - GL_POINTS and Stencil Buffer -

i trying draw texture in opengl es 2.0 using gl_points applying stencil buffer. stencil buffer should come texture. rendering results texture , presenting texture screen. here code rendering texture:

//initialize buffers, initialize texture, bind framebuffer ..... glclearstencil(0); glclear (gl_stencil_buffer_bit); glcolormask( gl_false, gl_false, gl_false, gl_false ); glenable(gl_stencil_test); glstencilfunc(gl_always, 1, 1); glstencilop(gl_keep, gl_keep, gl_replace); glbindtexture(gl_texture_2d, stencil); gluseprogram(program[program_point].id); gldrawarrays(gl_points, 0, (int)vertexcount); glcolormask(gl_true, gl_true, gl_true, gl_true); glstencilfunc(gl_never, 0, 1); glstencilop(gl_replace, gl_keep, gl_keep); glbindtexture(gl_texture_2d, texture); gluseprogram(program[program_point].id); gldrawarrays(gl_points, 0, (int)vertexcount); gldisable(gl_stencil_test); .... //render texture screen

the result getting texture beingness drawn without masking applied stencil. had few questions regarding issue:

is possible utilize stencil buffer gl_points? is possible utilize stencil buffer when rendering texture? does stencil texture have have special properties (solid colour, internal format...etc)? are there apparent mistakes code?

this result looking for:

update:

my problem, pointed out selected answer, did not attach stencil stencil attachment of fbo:

glframebufferrenderbuffer(gl_framebuffer, gl_stencil_attachment, gl_renderbuffer, stencilbufferid);

i did not know required when rendering texture. secondly not using proper stencil test.

glstencilfunc(gl_equal, 1, 1); glstencilop(gl_keep, gl_keep, gl_keep);

did job.

addressing questions in order:

is possible utilize stencil buffer gl_points?

yes. stencil test applied fragments, no matter of primitive type rendered. case write framebuffer without applying stencil test glclear().

is possible utilize stencil buffer when rendering texture?

yes. however, when render texture using fbo, stencil buffer of default framebuffer not used. have create stencil renderbuffer, , attach stencil attachment of fbo:

gluint stencilbufferid = 0; glgenrenderbuffers(1, &stencilbufferid); glbindrenderbuffer(gl_renderbuffer, stencilbufferid); glrenderbufferstorage(gl_renderbuffer, gl_stencil_index8, width, height); glframebufferrenderbuffer(gl_framebuffer, gl_stencil_attachment, gl_renderbuffer, stencilbufferid); does stencil texture have have special properties (solid colour, internal format...etc)?

opengl es 2.0 not have stencil textures. have utilize renderbuffer stencil attachment, shown in code fragment above. gl_stencil_index8 format supported renderbuffers can used stencil attachment. es 3.0 supports depth/stencil textures.

are there apparent mistakes code?

maybe. 1 thing looks odd never apply stencil test in code shown. while enable stencil test, utilize gl_always , gl_never stencil function. names suggest, these functions either or never pass stencil test. don't allow fragments pass/fail depending on stencil value. have expected before sec draw call:

glstencilfunc(gl_equal, 1, 1); glstencilop(gl_keep, gl_keep, gl_keep);

this render fragments current stencil buffer value 1, corresponds fragments rendered previous draw call.

ios objective-c opengl-es opengl-es-2.0 stencil-buffer