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Water Reflection and Opacity

4 posts in this topic

Hello again!

I'm having trouble with water opacity and reflection at the same time...

I can do them apart but not at the same time.

GLvoid DrawGLScene(GLvoid){
float look[3] = {0.0,0.0,0.0};

double eqr[] = {0.0f,0.0f, -1.0f, 0.0f}; // Plane Equation To Use For The Reflected Objects

gluLookAt(default_player->cam[0], default_player->cam[1], default_player->cam[2], look[0], look[1], look[2], 0, 0, 1);

glStencilFunc(GL_ALWAYS, 1, 1);


glStencilFunc(GL_EQUAL, 1, 1);
/* DRAW */

glClipPlane(GL_CLIP_PLANE0, eqr);
glScalef(1.0f, 1.0f, -1.0f);
glLightfv(GL_LIGHT1, GL_POSITION,default_player->light_pos);
gl_all_textures(hash_tex, default_player,map,1); /* terrain */
glLightfv(GL_LIGHT1, GL_POSITION,default_player->light_pos);


RenderWater(); /* reflection working but no opactity */
gl_all_textures(hash_tex, default_player,map,0); /* terrain */
// RenderWater(); /* opacity working but no reflection */



my goal is something like this:

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Well, I'm not sure if this will work or not, but assuming that you're using alpha values for the Water (or maybe you need alpha values for the reflection?), you should be enabling blending. Usually you use it like so, you can however use it many different ways though:

glEnable(GL_BLEND); // Enables blending for OpenGL

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); // Set the Blending function

There's a lot more OpenGL blending functions, but this might do the job, ask Google if you don't like it. [img]http://public.gamedev.net//public/style_emoticons/default/smile.png[/img]

FAQ on Transperancy:

Sorry if you already know this, it just doesn't seem like your enabling blending o:

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void RenderWater(){
static float wx=0, wy=0;

glBindTexture(GL_TEXTURE_2D, 5);
glColor4f(0.3, 0.3, 0.3, 0.6);
glTexCoord2f(-map->size+wx, -map->size+wy); glVertex3f (-map->size*0.5,-map->size*0.5,0.0);
glTexCoord2f(+map->size+wx, -map->size+wy); glVertex3f (map->size*0.5,-map->size*0.5,0.0);
glTexCoord2f(+map->size+wx, +map->size+wy); glVertex3f (map->size*0.5,map->size*0.5,0.0);
glTexCoord2f(-map->size+wx, +map->size+wy); glVertex3f (-map->size*0.5,map->size*0.5,0.0);
if(wx>8) wx-=8;
if(wy>8) wy-=8;

I enabled blend in RenderWater().

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The technique that you're using (where you use the stencil buffer to render the regular scene and the "mirrored" scene into the same render-target) is pretty old school.
To achieve robust transparency, I would recommend rendering the "mirrored" scene into a separate render-target, and then compositing the result on top of the regular scene.

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I found the following resource particularly useful, but you would have to convert to OpenGL and use shaders:


The explanation is pretty good though :)

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