ipad1 vs ipad2：不同的渲染結果與OpenGL

Question

當我在ipad1上運行我的應用程序時我看到不同的結果，然後當我在ipad2上運行相同的應用程序。我對屏幕中間的圖書大小感興趣。

iPad1 result

iPad2 result

我的代碼如下。

- (void)drawGallery{ 

glDepthFunc(GL_LESS); 
glEnable(GL_DEPTH_TEST); 

ResourceManager *rm = [ResourceManager sharedInstance]; 
GLuint currProgram = [rm getProgram:PROGRAM_BASIC_LIGHTNING]; 

glUseProgram(currProgram); 

glBindFramebuffer(GL_FRAMEBUFFER, framebuffer); 
glViewport(0, 0, 768, 1024 + 2 * GALLERY_OFFSET_Y); 

GLfloat modelviewProj[16]; 

for (Sheet *sh in self.interfaceManager.gallery.sheets){ 

    if ([self.interfaceManager.gallery shouldDrawSheet:sh]){ 

     [self MakePerspectiveMatrix:modelviewProj 
          OriginX:0.0 
          OriginY:0.0 
           Width:SCREEN_WIDTH 
          Height:SCREEN_HEIGHT 
          Rotation:sh.rotation 
         TranslationX:sh.translationX 
         TranslationZ:sh.translationZ 
          ScaleX:1.0 
          ScaleY:SCREEN_HEIGHT/(SCREEN_HEIGHT + 2 * GALLERY_OFFSET_Y)]; 


     vertexDataTextured *model; 
     if (sh.type == SHEET_TYPE_LEFT){ 
      model = (vertexDataTextured *)[rm getModel:MODEL_SHEET_LEFT]; 
     } else { 
      model = (vertexDataTextured *)[rm getModel:MODEL_SHEET_RIGHT]; 
     } 


     // update uniform values 

     glUniformMatrix4fv(basic_lighting_uniforms[BASIC_LIGHTING_UNIFORM_MODEL_VIEW_PROJECTION_MATRIX], 1, GL_FALSE, modelviewProj); 

     glUniform1f(basic_lighting_uniforms[BASIC_LIGHTING_UNIFORM_ROTATION], degreeToRadians(-sh.rotation)); 

     glActiveTexture(GL_TEXTURE0); 
     GLuint texture = [rm getTexture:TEXTURE_COLORING_PICTURE Index1:self.currentBook.number Index2:sh.number]; 
     glBindTexture (GL_TEXTURE_2D, texture); 


     glUniform1i(basic_lighting_uniforms[BASIC_LIGHTING_UNIFORM_TEXTURE], 0); 

     glVertexAttribPointer(BASIC_LIGHTING_ATTRIB_VERTEX, 3, GL_FLOAT, GL_FALSE, sizeof(vertexDataTextured), &model[0].vertex); 
     glEnableVertexAttribArray(BASIC_LIGHTING_ATTRIB_VERTEX); 

     glVertexAttribPointer(BASIC_LIGHTING_ATTRIB_TEX_COORDS, 2, GL_FLOAT, GL_FALSE, sizeof(vertexDataTextured), &model[0].texCoord); 
     glEnableVertexAttribArray(BASIC_LIGHTING_ATTRIB_TEX_COORDS); 

     glDrawArrays(GL_TRIANGLES, 0, 6); 

     if (![self validateProgram:currProgram]) { 
      NSLog(@"Failed to validate program: (%d)", currProgram); 
     } 
    } 
} 
} 

頂點着色器：

uniform mat4 modelViewProjectionMatrix; 
uniform float rotation; 
attribute lowp vec3 position; 
attribute lowp vec2 texCoords; 
varying lowp vec2 fTexCoords; 
varying lowp vec4 computed_color; 

void main() 
{ 
    fTexCoords = texCoords; 

    vec4 postmp = vec4(position.xyz, 1.0); 
    vec4 newposition = modelViewProjectionMatrix * postmp; 
    gl_Position = newposition; 

    vec3 ambient_color = vec3(0.5, 0.5, 0.5); 
    vec3 norm = vec3(sin(rotation), 0.0, cos(rotation)); 

    vec3 light_position1 = vec3(15.0, 0.0, 20.0); 
    vec3 light_direction1 = normalize(vec3 (0.2, 0.0, 1.0)); 
    vec4 light_diffuse_color1 = vec4 (0.4, 0.4, 0.4, 1.0); 
    float ndotl1 = max(0.0, dot(light_direction1, norm)); 
    vec4 temp_color1 = ndotl1 * light_diffuse_color1 * 15.0/(length(light_position1 - newposition.xyz)); 

    vec3 light_position2 = vec3(-30.0, 0.0, 25.0); 
    vec3 light_direction2 = normalize(vec3(-0.2, 0.0, 1.0)); 
    vec4 light_diffuse_color2 = vec4 (0.5, 0.5, 0.5, 1.0); 
    float ndotl2 = max(0.0, dot(light_direction2, norm)); 
    vec4 temp_color2 = ndotl2 * light_diffuse_color2 * 15.0/(length(light_position2 - newposition.xyz)); 

    computed_color = vec4(temp_color1.rgb + temp_color2.rgb + ambient_color, 1.0); 
} 

片段着色器：

precision lowp float; 
uniform sampler2D texture; 
varying vec2 fTexCoords; 
varying lowp vec4 computed_color; 

void main() 
{ 
    gl_FragColor = texture2D(texture, fTexCoords) * computed_color; 
} 

Answer 1

的問題是在lowp presicion用於位置。感謝Brad Larson。